CURRICULAM VITAE Academic Qualification -...

Curriculam Vitae

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CURRICULAM VITAE

Mr. Sanjay D. Gupta [email protected] Senior Research Fellow Ph: 91-9879666643

Academic Qualification B. Sc.: Physics, April 2005

Veer Narmad South Gujarat University, Surat, Gujarat M. Sc.: Physics (Secured First Rank), April 2008 Veer Narmad South Gujarat University, Surat, Gujarat. Ph. D.: Physics, M. K. Bhavnagar University, Gujarat. Under the supervision of Prof. Prafulla K Jha Skills.: Experiences of first-principles electronic-structure calculations

using DFT method implemented in PWSCF, ABINIT and VASP codes on parallel LINUX environment. Programming languages - C, FORTRAN.

Awards Awarded as Senior Research Fellow in DST-RFBR Major Research Project in December 2011.

Awarder as Junior Research Fellow in DST-RFBR Major Research Project in April 2009.

Awarded as Project Fellow in UGC Major Research Project In August 2008. Secured First Rank in M. Sc. Physics (2008). Won 1st Prize in Physics quiz competition, jointly organized by IAPT and GUJCOST.

Won 2nd Prize in inter College Quiz competition. Visited “Institute of Geology and Mineralogy, SBRAS, Novosibirsk, Russia during 6th July-18th July, 2009” Scientific collaboration within the frame work of Indo-Russia agreement.

International Visit Visited “Institute of Geology and Mineralogy, SBRAS, Novosibirsk, Russia during 6th July-18th July, 2009” Scientific collaboration within the frame work of Indo-Russia agreement.

Presented paper on “First principles study of structural, electronic and dynamical properties of lanthanum nitrides” organized by CECAM-Workshop “Graphene: From band structure to many-body physics”, 3-7th Sep. 2012, Bremen, Germany, Sanjay D. Gupta, Sanjeev K. Gupta, Prafulla K. Jha,

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List of Publications

International Publications

A First Principles Lattice Dynamics and Raman Spectra of the Ferroelastic Rutile to CaCl2 Phase Transition in SnO2 at High Pressure, Sanjay D. Gupta, Sanjeev K. Gupta, Prafulla K. Jha, N. N. Ovsyuk (In communication 2012).

Structural, Dynamical and Thermodynamical stability of Cadmium Nitride: An ab-initio Approach, Sanjay D. Gupta and Prafulla K. Jha (In communication 2012).

Superconductivity and phonon properties of transition metal nitrides: The group III-IV nitride crystals, Sanjeev K. Gupta, Sanjay D. Gupta and Prafulla K. Jha (In communication 2012).

Structural, electronic and dynamical stability of heavy Iron pernitride: A spin polarized first principles study Sanjay D. Gupta, Prafulla K. Jha (European Journal of physics: B DOI: 10.1140/epjb/e2012-301114-3).

Puzzling phonon dispersion curves and vibrational mode instability in superconducting MgCNi3, Prafulla K Jha, Sanjay D. Gupta, Sanjeev K. Gupta, AIP Advances 2, 022120 (2012).

Smearing induced dynamical stability of NbN and MoN in rocksalt structure, Sanjay D. Gupta, Prafulla K. Jha, Physica B: Physics of Condensed Matter, 407, 1978 (2012).

Pressure-induced phonon, electronic and thermal properties of antipervoskite AlCNi3 Prafulla K. Jha, Sanjay. D. Gupta, Sanjeev K. Gupta, International Conference on High Pressure Science and Technology September 25-30, 2011 Journal of Physics: Conference Series 377 (2012) 012089.

Pressure-induced vibrational and electronic properties of palladium per nitride, Sanjay. D. Gupta, Sanjeev K. Gupta, Prafulla K. Jha, International Conference on High Pressure Science and Technology September 25-30, Journal of Physics: Conference Series 377 (2012) 012078.

An abinitio study of ground state, electronic and thermodynamical properties of GaP and Ga2P, Journal of Thermal Analysis and Calorimetry, Himadri R. Soni, Venu Mankad, Sanjay D. Gupta, Sanjeev K. Gupta, Prafulla K Jha, 107, 39 (2012).

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High Pressure Study On the Phonon Spectra and Thermal Properties in Hafnium Nitride and Zirconium Nitride, Sanjay D. Gupta, Sanjeev K. Gupta, Prafulla K Jha, Journal of Thermal Analysis and Calorimetry 107, 49 (2012).

Density Functional Theoretical Study of the Structural, Electronic and Lattice Dynamical Properties of Platinum Pernitride Himadri R. Soni, Sanjay D. Gupta, Sanjeev K. Gupta and Prafulla K. Jha, Physica B: Physics of Condensed Matter 406, 2143 (2011).

Structures, electronic properties and phonons of platinum nitrides by density functional theory, Prafulla K. Jha, Sanjay D. Gupta, Sanjeev K. Gupta and D. Kirin Vol. 25, 11, 1543 (2011).

Stable Structure of Platinum Carbides: A First Principles Investigation on the Structure, Elastic, Electronic and Phonon Properties, Venu Mankad, Nikita Rathod, Sanjay D. Gupta, Sanjeev K. Gupta and Prafulla K. Jha, Materials Physics and Chemistry 129, 816 (2011).

A First-principles Lattice dynamical study of lanthanum nitride using density functional theory under pseudopotential approximation, Sanjay D. Gupta, Sanjeev K. Gupta and Prafulla K. Jha, Computational Materials Science 49, 910 (2010).

Corrigendum to „„First-principles lattice dynamical study of lanthanum nitride under pseudopotential approximation” Comput. Mater. Sci. 50, 810 (2010).

First-principles study of structural, electronic, elastic, phonon, and thermodynamical properties of the niobium carbide, Nikita Rathod, Sanjay D. Gupta Sanjeev K Gupta, Prafulla K. Jha, Solid State Phenomena 177, 67 (2011).

Publications in Conference

First principles study of structural, electronic and dynamical properties of lanthanum nitrides, Sanjay D. Gupta, Sanjeev K. Gupta, Prafulla K. Jha, CECAM-Workshop “Graphene: From band structure to many-body physics”, Bremen, Germany, 3-7th Sep. 2012.

High Pressure Raman Spectra of Rutile SnO2 using First Principles Calculation, Sanjay D. Gupta, Sanjeev K. Gupta, Prafulla K. Jha and N. N. Ovsyuk, (ICORS-2012, IISc Bangalore, 12-17August)

Analysis of structural and dynamical stability of XN2 (X=Sr, Ca) Pernitrides using Raman modes, Sanjeev K. Gupta, Sanjay D. Gupta, Prafulla K. Jha and N. N. Ovsyuk, (ICORS-2012, IISc Bangalore, 12-17August).Pressure Raman Spectra

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of Rutile SnO2 using First Principles Calculation,(Oral presentation) Sanjay D. Gupta, Sanjeev K. Gupta, Prafulla K. Jha and N. N. Ovsyuk, (M S University of Baroda, 22 Sept, 2012)

Energetic, Structural, Electronic and Lattice Dynamical Properties of LaN2: An Ab-initio Calculation, Sanjay. D. Gupta and Prafulla K. Jha, 3rd National Conference on Condensed Matter Physics, CMMP-2012, Vallabh Vidyanagar, Gujarat.

High Pressure Study On The Phonon Spectra In Hafnium Nitrides, Sanjay D. Gupta, Sanjeev K Gupta and Prafulla K. Jha, 55th DAE Solid State Physics Symposium (2010).

First-principles study of phonon properties in the series of III (Ti, V, Cr)-nitrides crystals, The Abdus Salam International Centre for Theoretical Physics “Spring College of Computational Nanoscience”, Sanjeev K. Gupta, Sanjay D. Gupta, P. K. Jha and S. P. Sanyal, Strada Costiera, Trieste, Italy May 16-28, 2010.

Properties of III-nitrides and phosphides at high pressure, S. Shinde, A. Pandya, Sanjay D. Gupta, and Prafulla K. Jha, Proceedings of the DAE Solid State Physics, Symposium, 54, 332 (2009).

Ab-initio calculation of phase stability of GaP and GaSb crystals at high pressure, Sanjay D. Gupta, Sanjeev K. Gupta and Prafulla K. Jha, Proceedings of the DAE Solid State Physics, Symposium, 54, 334 (2009).

Tailoring the size of ZnO Naoncrystal, International Conference on „Current Trends in Technology”, Nirma University (NUiCONE2010), Venu Mankad, Sanjay D. Gupta, Satyam Shinde, Shibu Pillai, Prafulla K. Jha (2010).

AIP ADVANCES 2, 022120 (2012)

Puzzling phonon dispersion curves and vibrational modeinstability in superconducting MgCNi3

Prafulla K. Jha, Sanjay D. Gupta, and Sanjeev K. GuptaDepartment of Physics, Bhavnagar University, Bhavnagar-364001, India

(Received 24 January 2012; accepted 20 April 2012; published online 2 May 2012)

A first principles calculation of the lattice dynamical properties of superconducting

MgCNi3 has been performed using density functional perturbation theory (DFPT).

The calculated phonon dispersion curves and phonon density of states have been

compared with inelastic x-ray scattering (IXS) and inelastic neutron scattering (INS)

measurements. We show for the first time that phonon dispersion curves for MgCNi3in whole Brillouin zone are positive (stable phonon modes) and in good agreement

with the experimental data. The phonon DOS shows absence of phonon density of

states at zero energy unlike earlier calculations. There is a good agreement between

calculated and experimental electron-phonon parameter and superconducting tran-

sition temperature. The Eliasberg function is quantitatively as well as qualitatively

different from the phonon density of states. The lattice specific heat and Debye

temperature do not show any anomalous behaviour. Copyright 2012 Author(s). This

article is distributed under a Creative Commons Attribution 3.0 Unported License.

[http://dx.doi.org/10.1063/1.4714366]

I. INTRODUCTION

The intermetallic MgCNi3 has attracted great attention due to the discovery of superconduc-

tivity at 8 K1 in it and its unusual characteristics in recently found series of superconductors.1–4

The superconductivity is unusual in view of the large content of Ni in the material, which would

normally favour a magnetic ground state. Thus, in the recent past several attempts have been made

to investigate the structural, electronic, vibrational and superconducting properties of MgCNi3.1, 4–14

Experimental results9, 15–17 have provided evidence for a medium to strong-coupling superconduc-

tivity driven by electron-phonon interactions. Further evidence for the phonon-mediated pairing

mechanism is provided by theoretical estimates ranging between 0.8 to 1.5.5, 9, 14 The electronic

structure measurements and calculations4, 9, 18–21 indicate the large density of states (sharp peak) just

below the Fermi level arising from an extended van Hove singularity which further supports the

strong electron-phonon coupling (EPC).4

A number of model and first principles investigations of lattice dynamics of MgCNi3 have

been performed.5–7, 14 The Ni- derived acoustic phonon modes due to their likely link with the

superconducting transition21 and instability of the acoustic phonon modes at some points in Bril-

louin zone are of special interest. All previous theoretical calculations including our own model

calculation7 show soft modes, anomalies and regions of imaginary (negative) frequencies. However,

detailed features and locations of these unstable modes in reciprocal space are very different. While

our own calculated phonon dispersion curves show the unstable acoustic modes at R- zone edge

point,7 the earliest ab-initio calculation performed by Ignatov et al.5 shows the same instability

between Ŵ- and M- points along with few dips near X- zone edge and in between Ŵ- and R- points.

The calculations of Heid et al.6 show that the instability appearing over a large area in reciprocal

space which is most pronounced near the X- and M- zone edges. Ab-initio calculations of Tutunce

and Srivastava14 show that the phonon modes with imaginary frequency are present between X- and

R- edge points along with a dip between R- and Ŵ- points for TA mode. Imaginary frequencies which

show instability of the dynamical structure and also unphysical particularly for a compound which

2158-3226/2012/2(2)/022120/9 C© Author(s) 20122, 022120-1

Smearing induced dynamical stability of NbN and MoN in rocksalt structure

Sanjay D. Gupta, Prafulla K. Jha n

Department of Physics, Bhavnagar University, Bhavnagar 364002, India

a r t i c l e i n f o

Article history:

Received 25 December 2011

Accepted 22 January 2012Available online 30 January 2012

Keywords:

Nitride

First principles calculation

Electronic temperature

Phonon

Dynamical stability

a b s t r a c t

The present paper reports a comprehensive first-principles calculation of electronic structure and

lattice dynamical properties of niobium and molybdenum mononitrides in rocksalt phase at ground

state as well as at finite electronic temperature applied using smearing parameter. The optimized

structure with equilibrium parameters in rocksalt phase is dynamically unstable. An increase in

smearing parameter or considering the finite temperature effects increases acoustic phonon frequen-

cies at X point of the Brillouin zone and rocksalt structure dynamically stabilized for both compounds.

This is because of the lowering of Fermi energy with increase of smearing parameter. Much better

agreement between the calculated and experimental data is found as compared to previous calculations

and a consistent description of the dynamical stability in the case of rocksalt phase of NbN and MoN is

achieved. The thermodynamical functions are also calculated in the frame work of quasi harmonic

approximation and discussed.

& 2012 Elsevier B.V. All rights reserved.

1. Introduction

The transition metal nitrides have attracted much scientific

importance over the last several years for basic research as well as

technology. This was motivated by their potential applications in

industry as cutting tools and in protective coating to hard coating

for magnetic storage devices due to their unusual and diverse

properties such as high hardness, chemical stability, high corro-

sion resistance etc., [1–5].

NbN and MoN exhibits long history up to current age of

theoretical studies of properties and phase transformation in

rock-salt stoichiometric structure. Density functional theory

(DFT) currently being the method of choice for first principles

studies of crystalline materials and have been used to address a

number of fundamental issues of structure and properties of

rocksalt phase of NbN and MoN [2–6]. However, the estimated

values of band gap, structural properties, vibrational spectrum

and electron–phonon interaction are multivalued and unclear

[3,6,7]. DFT calculations are usually performed in the thermal

limit at T¼0 K, while most of the nitrides like NbN and MoN in

rocksalt phase are difficult to stabilize at low temperature with-

out applying pressure or introducing dopants. The experimental

and theoretical studies probed a number of structural and vibra-

tional properties of NbN [1,8] and MoN [9] including pressure

induced changes in its phonon spectrum [2,10]. The Nb-N system,

mainly the NbNx exist in several phases such as NaCl type lattice,

tetragonal, hexagonal with anti WC type lattice and hexagonal

with anti NiAs type lattice [11,12]. We note few recent works

where the vibrational spectra of NbN and MoN is determined and

found that there are imaginary frequencies along the high

symmetry directions and several points in the Brillouin zone

[3–6,10]. Hart and Klein [13] have shown using linear augmented

plane wave method that the dynamical stability in MoN is not

mitigated and ever the application of pressure fails in fabricating

MoN in rocksalt due to phonon instability at X-point of the

Brillouin zone. Weber et al. [14] suggested that the phonon

anomalies arise due to the electronic transition between the W3

states which strongly increases a negative contribution to the

dynamical matrix for the phonon wave vector at X-point for NbN,

while Hart and Klein [13] found elastic constant C44 instability to

be responsible for the negative frequencies in the phonon disper-

sion curves. In spite of these investigations a number of open

issues remains unclear, in particular the dynamical instability of

NbN and MoN in rocksalt structure. It is observed that the

pressure alone could not bring out the dynamical stability in

these compounds [10,14]. In the case of MoN, the application of

pressure further increases the instability. Recently, Ivashchenko

et al. [10] have analyzed the stability of different phases of NbNx

on the basis of electronic band structure and phonon calculations

using smearing induced electronic temperature. They showed

that the phase could either be stabilized using electronic tem-

perature or nitrogen content. However, the electronic tempera-

ture is very high and corresponding pressure is not mentioned. It

is expected that the pressure would be low. Furthermore, a clear

range of electronic temperature or pressure for the stability of the

phase is not reported. Recently, it is shown that the consideration

Contents lists available at SciVerse ScienceDirect

journal homepage: www.elsevier.com/locate/physb

Physica B

0921-4526/$ - see front matter & 2012 Elsevier B.V. All rights reserved.

doi:10.1016/j.physb.2012.01.117

n Corresponding author. Tel.: þ91 278 2422650; fax: þ91 278 2426706.

E-mail address: [email protected] (P.K. Jha).

Physica B 407 (2012) 1978–1984

Pressure-induced phonon, electronic and thermal properties

of antiperovskite AlCNi3

Prafulla K. Jha, Sanjay D. Gupta and Sanjeev K. Gupta


E-mail: [email protected]

Abstract. First principle pseudopotential calculations were performed to investigate structural,

electronic, vibrational, and electron phonon interaction of antiperovskite AlCNi3. The stability of AlCNi3 in the antipervoskite phase has been analysed on the basis of the results of electronic

structure, electronic density of states and phonon calculation at ambient as well as hydrostatic

7.3 GPa high pressure. The dynamical stability, electron phonon interaction and

superconductivity have been discussed at ambient as well as hydrostatic high pressure 7.3 GPa.

1. Introduction

The discovery of 8 K superconductivity in the non-oxide perovskite MgCNi3 has attracted much

attention among intermetallic non-oxide perovskite cubic structure. At first glance, MgCNi3 should

belong to the list of unconventional superconductors due to its high content of magnetic element Ni. However, the nature of its superconductivity is still controversial [1-2]. In spite of this, the occurrence

of superconductivity through electron-magnon coupling spin fluctuations is found to be active in

determining the properties of both superconducting and normal state [2-3]. As an alternative, it is significant to investigate the materials property which are closely related to MgCNi3, i.e., AlCNi3

(A=Zn, Al, Ga, In, Cd, and so on). As to Al compound, previous experimental studies indicate

AlCxNi3 is nonmagnetic or PM [4-5], while a recent work shows a PM into weak FM transition at near 300 K in AlCNi3 [6]. In order to eliminate the discrepancy, more efforts are needed. Several

theoretical and experimental studies have been carried out on substitution of Mg with Al, Zn, in

MgCNi3, in order to determine the effect of such substitution on the superconducting transition temperature and dynamical stability. In recently the synthesis of AlCNi3 in which Al replaces Mg sites

of the superconducting intermettalic perovskite MgCNi3. Even though AlCNi3 isostructural with

MgCNi3 unfortunately the superconductivity has not been detected in these compound even when temperature lowered up to 4K. While a recent theoretical calculations shows that the calculated

phonon modes are unstable along the [110] and [111] symmetry direction in the Brillouin zone [7].

Motivated with this fact the dynamical instability and softening of acoustic phonon branch at high symmetry direction leads to the high temperature superconducting material. It is known that the

theoretical calculation on AlCNi3 [8] shows that the density of states at Fermi level is smaller than that

of MgCNi3 and it has been argued that a strongly defined DOS at the Fermi level could be responsible for the absence of superconductivity in the AlCNi3 non-oxide antiperovskite. It is therefore,

worthwhile to examine theoretically the structural, electronic and vibrational properties of

antiperovskite AlCNi3. The results of this investigation can reveal some useful insights towards the

23rd International Conference on High Pressure Science and Technology (AIRAPT-23) IOP Publishing

Journal of Physics: Conference Series 377 (2012) 012089 doi:10.1088/1742-6596/377/1/012089

Published under licence by IOP Publishing Ltd1

Pressure-induced vibrational and electronic properties of

palladium per nitride

Sanjay D. Gupta, Sanjeev K. Gupta and Prafulla K. Jha*


*E-mail: [email protected]

Abstract. We predict electronic and structural phase transition at 11GPa for crystalline PdN2

in pyrite structure by employing first principles calculation using density functional theory

implemented in Quantum Espresso code. The electronic band structure, equation of states and

dynamical properties at zero as well as high pressure are calculated within the frame work of

conventional GGA exchange correlation functional. We report the sharp change of the Pd-N

and N-N bond length at phase transition pressure in support of isostructural phase transition

driven by electronic phase transition for PdN2 in pyrite structure. The calculated Raman

frequencies near the phase transition pressure reveals the first order isostructural phase

transition by the instability of longitudinal acoustical as well as optical branches, provides the

mechanism for experimentally observed decomposition below 13GPa.

1. Introduction

Metallic nitrides are of great technological and fundamental importance due to extraordinary

properties such as hardness, superconductivity, photoluminescence and many type of magnetism [1].

Traditional applications have taken advantage of the hard and refractory nature of many of these

compounds, but numerous mere recent applications are based on their crystalline structure stability,

electronic and vibrational properties [2]. Now a consensus has been reached concerning the observed

crystal structure and stoichiometry i.e. one metal atom for every nitrogen dimmer [1-4]. However, it

was found that pyrite PdN2 structure decomposes at pressure below ~13GPa [3-5]. Therefore, the

correct stoichiometry could not be determined using electron microprobe or X-ray photoelectron

spectroscopy. Until now the crystalline structure of this new synthesized palladium per nitride has not

been determined. All noble metal nitrides (PtN2, IrN2 and OsN2) studied to date possess uncomplicated

behaviour due to significant hybridization between 5d electrons and N-2p electrons at all hydrostatic

pressure [6-8]. They are recoverable to ambient conditions after synthesis at high pressure and high

temperature [in the range of 60GPa and 2000K]. In contrast to these compounds, the synthesized

crystalline PdN2 at high pressure and temperature does not appear to be recoverable at ambient

conditions and decomposed below 13GPa [9]. Recently, Aberg et al. [4] have argued that the equation

of states (EOS) cannot be accurately described within either the local density or generalized gradient

approximations for PdN2 and only the Heyd-Scuseria-Ernzerhof exchange-correlation functional

(HSE06) provides very good agreement with experimental data. Motivated with this report, we have

investigated the EOS, electronic band structure phase transition and vibrational properties using

conventional generalized gradient approximations and analyzed with available experimental and

theoretical data. Our analysis concludes that the conventional GGA is sufficient to predict the physical

properties of PdN2 comparable to the experimental observation. We are able to observe the

decomposed below 13GPa similar to experiment.

2. Computational Methodology

We have investigated structural, electronic, and lattice dynamical properties using the plane wave

pseudopotential within the GGA-XC functional as parameterized by Perdew, Burke, and Ernzerhof for

treating the effects of exchange correlation implemented in PWSCF package. The Brillouin zone

integrations were performed using 6 6 6 Monkhorst-Pack k-point sampling for structural

relaxations and the calculation of other properties. The plane-wave cutoff was set to 38Ry, and

23rd International Conference on High Pressure Science and Technology (AIRAPT-23) IOP Publishing

Journal of Physics: Conference Series 377 (2012) 012078 doi:10.1088/1742-6596/377/1/012078

Published under licence by IOP Publishing Ltd1

An ab initio study of ground state, electronic

and thermodynamical properties of GaP and Ga2P

Himadri R. Soni • Venu Mankad • Sanjay D. Gupta •

Sanjeev K. Gupta • Prafulla K. Jha

29th STAC-ICC Conference Special Chapter

Ó Akademiai Kiado, Budapest, Hungary 2011

Abstract In the present paper, we report an ab initio

calculation of the ground state, electronic and thermody-

namical properties like constant volume lattice specific

heat, vibrational energy, internal energy, and entropy for

GaP and Ga2P is presented. These properties are obtained

after calculating the phonon spectrum over the entire

Brillouin zone. The calculations were performed using the

ABINIT program package, which is based on density

functional theory (DFT) method and the use of pseudo-

potentials and plane wave expansion. Difference in the

ground state properties such as electronic structure and

thermodynamical properties are discussed. The thermody-

namical properties follow the expected trend. There is a

good agreement between present theoretical and limited

available experimental data in the case of ground state such

as lattice constant and bulk modulus and electronic prop-

erties. With the increase of Ga atoms in the unit cell the

semiconducting nature of Ga2P turns to metallic. There is a

noticeable difference in the thermodynamical properties in

the case of both gallium compounds.

Keywords Thermal properties � Semiconductor � Density

functional theory � Band structure

Introduction

The chemistry and physics of the compounds formed by

the elements in groups III and V is extraordinarily rich and

their usefulness in the semiconductor industries has been a

motivation for numerous experimental and theoretical

studies. An increasing interest to investigation of clusters is

determined by the fact that cluster systems represent an

intermediate state between atoms and bulk metals. Prop-

erties of clusters strongly depend on size, which provides a

potential ability of application of clusters in nanotechnol-

ogies. Moreover, clusters can be considered as models of

surface and thin films, and cluster models are widely used

for investigation of adsorption and heterogeneous catalysis

[1]. The study of materials and their thermodynamical

properties is experiencing recent activity because of its

fundamental research interest and technological applica-

tions in the field of microelectronics and optoelectronics, as

a substrate for high speed electrical and optoelectronic

devices, optical switches, and so on [2, 3]. The compre-

hension of mechanisms of fabrication processes such as

chemical etching depends on the thermodynamic and

kinetic data of the chemical species, which in turn require

elucidation of the low-lying states of these species. Fur-

thermore, theoretical and experimental studies of such

clusters provide significant insight into the properties of

these species as a function of their sizes, as these species

exhibit significant variations in their properties.

In these structures, each atom is tetrahedrally bonded

to its first neighbors [2, 3]. The gallium arsenide clusters

of the general formula GaxAsy using laser-vaporization of

gallium arsenide crystal has been generated recently [4].

The photofragmentation pattern of these clusters also

deviated from the corresponding patterns of the group IV

clusters as a function of their sizes. In this regard, photo-

electron spectroscopy (PES) has proven to be a very

useful technique for studying the electronic and vibra-

tional structures of mass-selected clusters [5, 6]. One of

the key problems in the investigation of clusters is the

H. R. Soni � V. Mankad � S. D. Gupta � S. K. Gupta �

P. K. Jha (&)

Department of Physics, Bhavnagar University,

Bhavnagar 364022, India

e-mail: [email protected]; [email protected]

123

J Therm Anal Calorim (2012) 107:39–44

DOI 10.1007/s10973-011-1466-0

Author's personal copy

High pressure study on the phonon spectra and thermal

properties in hafnium nitride and zirconium nitride

Sanjay D. Gupta • Sanjeev K. Gupta •

Prafulla K. Jha

29th STAC-ICC Conference Special Chapter

Ó Akademiai Kiado, Budapest, Hungary 2011

Abstract We report ab initio calculations of the thermal

properties for transition metal nitrides, hafnium and zirco-

nium nitride at ambient and high pressures. The assessment

of thermodynamical properties like lattice specific heat,

vibrational energy, internal energy and entropy for two

nitrides has been carried out. The basic calculations of

ingredient phonon density of states for the determination of

thermal properties have been done using density functional

perturbation theory including external perturbations like

strains and electric fields in periodic systems. The ground

state properties such as equilibrium lattice constants and bulk

modulus obtained for two nitrides are in good agreement

with the available experimental value. The calculated pres-

sure variation of the phonon density of states shows trend

similar to the experimental pressure dependent Raman

spectra. The lattice specific heat, internal energy, entropy

and Helmholtz energy increases with pressure.

Keywords Density functional theory � Phonon density

of states � High pressure � Thermal properties

Introduction

The early transition metal mononitrides crystallize in the

rock-salt structure and are known as refractory compounds.

They exhibit extreme and unique physical properties of

hardness, brittleness, high melting point, and in several of

these compounds, a relatively high superconducting tran-

sition temperature [1]. Because of these properties, they

have technological applications in the area of hard coatings

for cutting tools and magnetic storage devices. Recently,

these compounds are also being investigated to understand

their role in thermoelectric applications [2, 3]. The ther-

moelectric applications and high melting point of any

material is the consequence of some special characteristics

of phonon spectra and hence the phonon dispersion curves,

thermal properties such as lattice specific heat, internal

energy, entropy, etc. are of great importance. Recently, the

phonon dispersion curves of HfN and ZrN have been

obtained using inelastic neutron scattering which shows

anomalous behaviour such as steep slopes of acoustic

phonon branches near zone centre of Brillouin zone and a

large gap between optic and acoustic phonon branches.

This anomalous character of phonon dispersion leads to

hardness and high melting point. Despite a direct correla-

tion between the phonon spectra which enhance the ther-

mal properties. Recently, there is a serious attention to the

thermal properties and phonon spectra of these nitrides

particularly at high pressure as it plays an important role in

the synthesis of this group of the compounds [3]. The

platinum nitride has been synthesized at high pressure and

high temperature. Recently, there are few reports on the

high pressure Raman spectra for HfN and ZrN [4, 5]. In

this article, we report a systematic study on the pressure

dependence of the phonon spectra and thermal properties

of two transition metal nitrides using first principle calcu-

lations under the frame work of density functional theory

(DFT).

Computational method

Theory and computational aspects of our computational

methods are based on the DFT. The first principles

S. D. Gupta � S. K. Gupta � P. K. Jha (&)

Department of Physics, Bhavnagar University, Bhavnagar

364022, Gujarat, India

e-mail: [email protected]

123

J Therm Anal Calorim (2012) 107:49–53

DOI 10.1007/s10973-011-1691-6


Density functional theoretical study of the structural, electronic and lattice

dynamical properties of platinum pernitride

Himadri R. Soni a, Sanjay D. Gupta a, Sanjeev K. Gupta b, Prafulla K. Jha a,n

a Department of Physics, Bhavnagar University, Bhavnagar 364022, Indiab Dipartimento di Fisica, Universit �a di Modena e Reggio Emilia and S3 National Research, Centre of CNR-INFM via Campi 213/A-41125 Modena, Italy


Article history:

Received 28 December 2010

Accepted 10 March 2011Available online 15 March 2011

Keywords:

Platinum pernitride

Pyrite

First principles

Phonons

Electronic band structure

a b s t r a c t

In the framework of density functional theory, the structural, electronic and lattice dynamical

properties of platinum pernitride have been investigated using the plane wave pseudopotential within

the GGA and LDA functional for treating the effects of exchange correlation implemented in PWSCF and

ABINIT packages. The computed lattice constant and bulk modulus agree well with the experiment and

other theoretical calculations. Both packages and correlation functional agree well on the lattice

constant within the deviation of about 1.6%. The bulk modulus has been quite successfully predicted by

LDA. The electronic structure and DOS of platinum pernitride show a narrow gap and confirms

semiconducting nature of this compound. The lattice dynamical calculation shows that the platinum

nitride in pyrite structure (platinum pernitride) is dynamically stable. The zone center phonon

frequencies particularly the Raman active phonons agree well with the experimental Raman data in

the case of GGA implemented in PWSCF. The pressure variation of Raman active modes shows a linear

variation; however, at higher pressure the variation is fast.

& 2011 Elsevier B.V. All rights reserved.

1. Introduction

The newly synthesized platinum nitride compound [1], the

first binary nitride of the noble metals group has not only

generated the significant interest for itself, but also to other

nitrides and carbides of this group [2–30] due to their excellent

physical, chemical and mechanical properties. Various theoretical

studies [22–30] have been performed in last few years to under-

stand the structural, electronic, elastic and vibrational properties

of newly synthesized platinum nitride [1]. However most of these

studies of platinum nitride done until the one by Young et al. [22]

were contradicting in concern of the suggested structure and

stoichiometry. The suggested structure in all earlier studies have

been based on the comparison of calculated and measured ground

state properties such as lattice parameter, bulk modulus, zone

center phonons and pressure variation of zone center Raman

active phonons. The X-ray diffraction study [1] predicts rock salt

as well as zinc blende structure (cubic symmetry) for platinum

nitride synthesized at high pressure and high temperature.

However the zinc blende phase was ambiguously concluded with

Pt:N as 1:1 and ruled out the rock salt phase, as the X-ray

diffraction cannot determine the positions of the nitrogen atoms

due to large mass difference in platinum and nitrogen. This was

followed by several theoretical studies suggesting zinc

blende [3,4,7,9,10,15, 16,19,22,29], rocksalt [3,4,9,15,16,19,22,29]

and the fluorite structure [7,10,12,18,22,29] for this newly

synthesized noble metal nitride, without satisfying simulta-

neously the mechanical and structural stability conditions for a

solid. The zinc blende phase satisfies the elastic stability condi-

tions and there is a good agreement of lattice constant with

the experimental value but the bulk modulus value is quite

lower in comparison to experiment [1] and other theoretical

work [3,4,7,9,10,15,16,19,22,29]. The calculated bulk modulus

and lattice constant in fluorite structure [7,10,12,18,22,29] of

platinum nitride are close to the experiment in comparison to

the zinc blende and rocksalt structures. As far as the observed

phonon modes using Raman spectroscopy in original work [1] are

concerned none of these works focus on this aspect. Therefore, a

comprehensive study on the PtN2 compound was desirable to

investigate the structural, mechanical and phonon properties in

good agreement with experimental observations. The literature

shows that the most of the studies on platinum nitride done until

the one by Young et al. [22] failed in reaching any conclusion on

the structure and stoichiomly. The study of Young et al. [22] has

been quite successful in this regard and based on the calculated

structural, electronic and phonon properties reaching more or less

a consensus on the crystal structure and stoichimetrices (Pt

atom:N atom¼1:2). They concluded that the platinum nitride

compound is formed in the pyrite structure with formula PtN2.

However, they failed in predicting the values of bulk modulus,

phonons, lattice parameters, etc. simultaneously in good agree-

ment with the experimental values. The bulk modulus and lattice

parameter values deviate about 10% and 0.91%, respectively, from

Contents lists available at ScienceDirect

journal homepage: www.elsevier.com/locate/physb

Physica B

0921-4526/$ - see front matter & 2011 Elsevier B.V. All rights reserved.

doi:10.1016/j.physb.2011.03.018

n Corresponding author.

E-mail address: [email protected] (P.K. Jha).

Physica B 406 (2011) 2143–2147

DOI: 10.1142/S0217979211100382

International Journal of Modern Physics BVol. 25, No. 11 (2011) 1543–1551c© World Scientific Publishing Company

STRUCTURAL AND ELECTRONIC PROPERTIES AND

PHONONS OF PLATINUM NITRIDES BY DENSITY

FUNCTIONAL THEORY

PRAFULLA K. JHA∗,‡, SANJAY D. GUPTA∗, SANJEEV K. GUPTA∗ and DAVOR KIRIN†

∗Department of Physics, Bhavnagar University, Bhavnagar 364 022, Gujarat, India†Ruder Boskovic Institute Bijenicka Cesta 54, P. O. B. 180, HR-10002 Zagreb, Croatia

‡[email protected]

Received 6 February 2009Revised 28 July 2009

Using first principles calculations, we provide here a unified study of structural and elec-tronic properties along with frequency of phonon modes at some high-symmetry pointsof the Brillouin zone for the noble metal nitride platinum nitride (PtN) by using PWSCFcode. Our calculations are performed for two phases viz. zincblende and rocksalt. Thepresent study predicts the zincblende structure as the most probable crystal structureout of two, besides it being metallic. The calculated structural and electronic propertiesand zone centre phonon modes are in good agreement with the experimental and othercalculated data.

Keywords: Density functional theory; noble metal nitride; electronic structure; phonons.

PACS numbers: 71.20.Ps, 81.05.Zx, 71.15.Mb

1. Introduction

The transition metal nitrides, commonly referred to as refractory metals, possess

an unusual combination of physical and chemical properties that are responsible

for many fundamental and technological applications.1–8 They are also of much

interest in catalysis, as electrode materials for batteries and fuel-cells, and as

superconductors.4–6 Most of these transition metals can form stable nitrides at high

temperatures and either at ambient or high pressure. Despite the wide interest and

applications of nitrides, only the nitrides of early transition metals were studied.7,8

However, the synthesis of platinum nitride has been made possible recently under

high pressure and temperature by Gregoryanz et al.9 and using laser-heated dia-

mond anvil cells by Crowhurst et al.10 The bulk modulus for this late transition

metal nitrides is remarkably high, 372 GPa,9 about 100 GPa higher than that for

pure Pt. This was further followed by the synthesis of IrN2 and OsN2, with a high

bulk modulus of 428 and 358 GPa, respectively.10–12 These works therefore have

important implications for high pressure research, particularly the possibility to

1543


Materials Chemistry and Physics 129 (2011) 816– 822


Materials Chemistry and Physics

jo u rn al hom epage : www.elsev ier .com/ locate /matchemphys

Stable structure of platinum carbides: A first principles investigation on the

structure, elastic, electronic and phonon properties

Venu Mankad a, Nikita Rathod a,b, Sanjay D. Gupta a, Sanjeev K. Gupta a, Prafulla K. Jha a,∗

a Department of Physics, Bhavnagar University, Bhavnagar 364022, Indiab Department of Physics, Vadodara Institute of Engineering, Vadodara 391510, India


Article history:

Received 25 November 2010

Received in revised form 29 March 2011

Accepted 9 May 2011

Keywords:

First principles

Structure

Elastic

Electronic structure

Phonons

Density of states

a b s t r a c t

A comprehensive first principles study of structural, elastic, electronic, phonon and thermodynamical

properties of novel metal carbide, platinum carbide (PtC) is reported within the density functional the

ory scheme. The ground state properties such as lattice constant, elastic constants, bulk modulus, shear

modulus and finally the enthalpy of PtC in zinc blende (ZB) and rocksalt (RS) structures are determined.

The energy band structure and electron density of states for the two phases of PtC are also presented.

Of these phases zinc blende phase of PtC is found stable and phase transition from ZB to RS structure

occurs at the pressure of about 37.58 GPa. The phonon dispersion curves and phonon DOS are also pre

sented. All positive phonon modes in phonon dispersion curves of ZBPtC phase indicate a stable phase

for this structure. Within the GGA and harmonic approximation, thermodynamical properties are also

investigated. All results reveal that the synthesized PtC would favor ZB phase. The compound is stiffer

and ductile in nature.

© 2011 Elsevier B.V. All rights reserved.

1. Introduction

There is currently a growing interest in platinum carbide (PtC)

due to the potential of transition metal carbides for basic research

and technological applications [1–3]. Platinum carbide belongs to

the group known as refractory compounds and it possess promising

characteristics such as high stiffness, high hardness, high thermal

conductivity and high melting temperature. Most of the earlier

experimental and theoretical works focused on groups IV and V

transition metal carbides (TMCs) [4–8] due to difficulties in syn

thesizing the noble metal carbides [8,9]. Recently, Ono et al. [10]

have synthesized the PtC at high temperature and high pressure

and found that the compound crystallizes in rocksalt (RS or B1)

phase with high bulk modulus of 339 GPa. But its structure has been

always an issue, particularly in the light of another recently syn

thesized transition metal compound namely the platinum nitride

(PtN) [11]. While, the Xray diffraction suggests the cubic symmetry

with rocksalt type structure for PtN, the zinc blende (ZB) structure

is concluded from the Raman spectroscopy for PtN as the first order

Raman spectra is forbidden in the case of cubic rocksalt structure.

The Raman spectra or phonon spectrum is an important criterion to

confirm the structure, particularly for the compounds of large mass

difference between anion (Pt) and cation (C or N) as it is difficult to

∗ Corresponding author. Tel.: +91 2782422650; fax: +91 2782426706.

Email addresses: [email protected], [email protected] (P.K. Jha).

distinguish between the zinc blende and rocksalt structures solely

from the Xray diffraction intensities [12,13].

The structural stabilities, ground states and electronic proper

ties of PtC compound have been studied recently using theoretical

methods [14–17] but the contradiction on its structure is still to be

resolved. Li et al. [14] using plane wave pseudo potential based

on first principles calculation found zinc blende structure to be

mechanically (satisfying the condition for elastic stability) more

stable, while Fan et al. [15,16] suggested rocksalt phase of PtC to

be more mechanically stable. They found a reasonably good agree

ment on the compressibility behavior of rocksalt PtC (RsPtC) with

the experiment. They also suggested that a metastable RS structure

may transfer to the more stable ZB structure under certain condi

tions based on the enthalpy and partial electronic density of states

(DOS) [16]. The phase transition pressure from ZB to RS structure

using abinitio plane wave pseudopotential density functional the

ory is reported separately as 52 GPa and 51.7 GPa by Li et al. [14]

and Peng et al. [17] respectively. Deligoz et al. [18] found that the ZB

phase of PtC transforms to the RS phase at about 42 GPa. Rabah et al.

[19] have performed fullpotential linearized muffintin orbital cal

culation for different phases of platinum carbide and showed that

the PtC is stable in zinc blende phase at zero pressure.

A considerable number of studies have been carried out on

the structural and electronic properties of the PtC, but its lattice

dynamical properties are still missing despite its importance to

confirm the structure. The full phonon properties not only play

a significant role in the studies of a wide variety of physical

02540584/$ – see front matter © 2011 Elsevier B.V. All rights reserved.

doi:10.1016/j.matchemphys.2011.05.014

First-principles lattice dynamical study of lanthanum nitride under

pseudopotential approximation

Sanjay D. Gupta, Sanjeev K. Gupta, Prafulla K. Jha *,1

Department of Physics, Bhavnagar University, Bhavnagar 364 022, India


Article history:

Received 26 April 2010

Received in revised form 28 June 2010

Accepted 30 June 2010

Available online 27 July 2010

Keywords:

First principles

Phonons

Structure

Electronic structure

Density of states

a b s t r a c t

The present paper reports a comprehensive first-principles calculation of lattice dynamical properties of

lanthanum nitride, using the relativistic separable dual-space Gaussian pseudopotentials and local den-

sity approximation. Our results concerning equilibrium lattice parameter and bulk modulus agree well

with the available experimental and previous theoretical data. The phonon dispersion curves and related

properties in both ambient rocksalt (RS) and high pressure cesium chloride (CsCl) structures are reported

for the first time which shows rocksalt as more stable structure similar to other calculations. The elec-

tronic and mechanical properties are also discussed.

Ó 2010 Elsevier B.V. All rights reserved.

1. Introduction

The study of transition metal nitride, lanthanum nitride (LaN)

has attracted extensive interest for basic research as well as for

technology because of its wide technological applications resulting

from its high hardness, brittleness, high melting point and super-

conducting transition temperature [1]. LaN is also interesting from

its optical, electronic, magnetic, mechanical and vibrational prop-

erties point of view [2–8]. LaN crystallizes in rocksalt structure

with spacegroup Fm3m (2 2 5) and belongs to the 5d transition

metal group with many problems primarily related to stoichiome-

try [4]. The different measured data on electronic properties indi-

cates different behavior from semi-metallic or half metallic to

semi-conducting for this transition metal nitride [9–11]. In order

to achieve a better understanding of their physical properties and

to the experimental discrepancies, some theoretical investigations

have been undertaken. From the available literature a clear contro-

versy exists between the studies carried out in the density func-

tional theory. Hasegawa [8] reported a band overlap of 9 mRy

from the augmented plane wave (APW) bandstructure calculation,

while Norman et al. [9] found that the LaN is a semimetal with a

band overlap of approximately 40 mRy (0.5442 eV). The electronic

structure calculation in B1 phase indicates semi-metallic nature

using GGA but contradict to the calculation of Stampft et al. [6]

which reports a band gap of 0.75 eV based on the screened ex-

change LDA calculations. The total electronic DOS reflects the

metallic nature of LaN. Vaitheeswaran et al. [3] from their high

pressure studies using tight-binding linear muffin-tin orbital

method (TB-LMTO) predict a structural transformation from the

rocksalt (B1) to CsCl (B2) phase at 26.9 GPa. They also reported

the superconductivity in LaN. A large number of theoretical studies

on structural phase transition confirm the transition from B1 to B2

phase under pressure but the phase transition pressure values vary

[2,12,13,15]. Ciftci et al. [2] predicted the structural phase transi-

tion from B1 to B2 structure at 25.25 GPa for LaN. They also calcu-

lated the band structure and elastic properties for both zero and

high pressure phases. The phase transition pressure is close to

the earlier theoretical reported values. However, there is a lot of

variation in the reported elastic constants along with the phase

transitions pressure [12–16].

As far as the phonon properties of LaN is concerned the earliest

work of lattice dynamics in rocksalt phase have been published by

Gökoglu and Erkisi [12]. They have reported the phonon dispersion

curves and elastic constants of LaN using plane-wave pseudopo-

tentials method of the density functional theory with generalized

gradient approximation (GGA). They observed phonon softening

and negative frequencies along with the large lattice anisotropy

even for their stable rocksalt phase. The observed instability in

phonon modes indicates for a very small or negative value of elas-

tic constants which is not observed. Furthermore, the degenerate

acoustic modes tend to a negative value even at the zone centre

(C-point) of the Brillouin zone (BZ). These observations are strange

for a stable structure and one should expect these instabilities only

0927-0256/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.

doi:10.1016/j.commatsci.2010.06.046

* Corresponding author. Tel.: +91 278 2422650; fax: +91 278 2426706.

E-mail addresses: [email protected], [email protected] (P.K. Jha).1 Present address: Institute of Theoretical Physics, Chinese Academy of Sciences,

Beijing 100 190, PR China.

Computational Materials Science 49 (2010) 910–915


Computational Materials Science

journal homepage: www.elsevier .com/locate /commatsci

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