e-

Inner region

Outer region

Jonathan Tennyson

Quantemol

University College London

UCL

April 2014

Electron collisions for

technological plasma models

Founded in 2004 as a University College London spin-off providing user friendly interfaces for sophisticated academic codes

Distribute 3 software packages:

UK R-matrix Code

GlobalKin Code Feedstock gases

Power Heat

Waste products

HPEM Code

User friendly interface on top of Kushner’s HPEM

VS

2D results

1D graphs and EEDF

Data export for comparison

Power coupling: CCP

Ar/Cl2: 0.8/0.2

2Freq: 10 MHZ 500 W 100 MHZ 750 W

Flow: 300 sccm

Electron kinetics: Monte-Carlo Solver

Wafer Size: 300 mm Chemistry: 10 species, 37 reactions

Running time: approx. 1 to 1.5 days

Electron Density Distribution

Extensively validated

and widely used in

industry

Uniquely designed for

simulation of low

pressure plasma

Has large variety of

physical model options

Released: March 2014

Intuitive interface

Multiple visualisation

capability

Easy-to-use reactor “painter”

Example library

Job runner with single and

simultaneous queuing

Parameter optimization

capability

An Introduction to the

programme

Processes: at low impact energies

Elastic scattering

AB + e AB + e

Electronic excitation

AB + e AB* + e

Dissociative attachment / Dissociative recombination

AB + e A + B

A + B

Vibrational excitation

AB(v”=0) + e AB(v’) + e

Rotational excitation

AB(N”) + e AB(N’) + e

Impact dissociation

AB + e A + B + e

Impact ionization (e,2e)

AB + e AB + e + e

Processes: at low impact energies

Photoionisation

AB + hn AB+ + e

All go via (AB)** . Can also look for bound states

Also consider:

New feature in

H H

Inner region

Outer region R-matrix

boundary

The R-matrix method J. Tennyson, Electron - molecule

collision calculations using the R-matrix

method, Phys. Rep., 491, 29 (2010).

e-

Electron – water rotationally resolved cross sections:

Differential cross sections (DCS) at 6 eV

DJ=1

DJ=0

DJ=all

*

Cho et al (2004)

Jung et al (1982)

R-matrix (2004)

A. The UK Molecular R-Matrix Codes

• Freely available online

• People can join as users on CCPForge

• Comprehensive but hard to use

(Can take a whole PhD (3 years) to correctly run one molecule!)

B. Quantemol-N

• Easy to use graphical interface

• Very simple input, requires little scientific knowledge or training

• Extra features (ionisation, dissociative attachment estimator,

high energy electronic excitation, etc)

Two methods of doing R-matrix calculations:

CCPQ Collaborative Computational Project Q - Quantum Dynamics

Main advantages of using Quantemol-N:

User friendly interface, which vastly

simplifies setting up an R-matrix simulation.

Full tutorial system to reduce learning curve.

Library containing 40+ examples.

Easy to use results format.

24/7 service support from Quantemol team.

Quantemol-N 4.1 can calculate:

Elastic cross-sections

Electronic excitation cross-sections (extended to high energies with BEf)

Super-elastic cross-sections between excited states

Electron impact dissociation

Scattering reaction rates

Resonance parameters

Dissociative electron attachment cross-sections estimator

Differential cross-sections

Momentum transfer cross-sections

Rotational excitation cross-sections

Atomic cross-sections

Electron impact ionisation at all energies

Red: features not in standard code

Examples obtained using

Quantemol-N

Chlorine – Dissociative Attachment

DZP basis for the target and frozen bond-length of 1.988Angstrom.

CAS-CI representation: 20 core electrons are frozen (Cl 1s, 2s and 2p orbitals).

14 active electrons are distributed as: (4 - 6σg, 4 - 5σu, 2πu, 2πg)14.

Lowest virtual orbitals of σg, σu and πu retained in the scattering calculation

48 target states in the close-coupling expansion.

Dissociative electron attachment cross sections for Cl2

Calculations used the DEA cross section estimator in Quantemol-N

Oxygen – Dissociative Attachment

Calculations: 6-311G* target basis at frozen bond length of 1.2144 A.

Target CAS: 4 core electrons frozen,and10 electrons in 12 valence orbitals:

(1σg, 1σ

u)4 (2σ

g, 3σ

g, 2σ

u, 3σ

u, 1π

u, 2π

u, 1π

g)12.

Scattering calculation augmented with the 4σg, 4σ

u and 2π

g orbitals.

48 states retained in close-coupling expansion.

Silane Ramsauer–Townsend minimum and

other features in good agreement

with experiment and theory

CF2 radical

-Highly reactive and therefore difficult species to

work with in the laboratory

R-matrix calculation

- Equilibrium geometry (C2v point group)

- Target Gaussian basis set: cc-pVTZ

- Included 8 target states

- Level: Full valence CI (MCSCF orbitals)

- R-matrix radius: 10 a0

CF2 radical

CF2 radical

Thanks for listening

UK R-matrix Code

GlobalKin Code Feedstock gases

Power Heat

Waste products

HPEM Code

Thank you for listening!

Some useful websites:

http://cccbdb.nist.gov/ - Good for

geometries, data comparisons

https://bse.pnl.gov/bse/portal - Basis set

database

Contact: Anna Dzarasova, +44 (0) 207 679 34 76, anna@quantemol.com

Methane

Electron – water (rotationally averaged)

elastic cross sections

Integral cross section

A Faure, JD Gorfinkel & J Tennyson, J Phys B, 37, 801 (2004)

Neopentane -17 atoms - no previous theory - Ramsauer-Townsend (RT) minimum at ~0.2eV in good agreement with experiment. - Bigger molecules are possible.

Electron – water Momentum transfer cross section

Cho et al (2004)

Johnstone & Newell

CF2 C6H6 C5H12 SiH4

Cl2 C3H4 NO2 C2H6

O2 C2 NO C3H8

H2O C3H6 O3 HCN

H3+ CaF+ PH3 HNC

CH4 CaF BF3 SiO

C3N CF N2 CS

Cl2O CO2 CO F2

CONH3 BF3 H2 HBr

Progress...

... plus a whole host of work done elsewhere.

Dominant interactions Inner region: can write exact H

Exchange

Correlation Adapt quantum chemistry codes

Outer region Long-range multipole polarization potential

Adapt electron-atom codes

High l functions required

Integrals over finite volume

Include continuum functions

Special measures for orthogonality

CSF generation must be appropriate

Many degenerate channels

Long-range (dipole) coupling

Boundary Target wavefunction has zero amplitude

R-matrix method for electrons: inner region wavefunction

Yk = A Si,j ai,j,k fiN hi,j + Si bj,k fj

N+1

fiN= target states = CI target built from nuclear centred GTOs

fjN+1= L2 functions

H H

e inner region

hi,j = continuum orbitals = GTOs centred on centre of mass

(within the Fixed-Nuclei approximation)

a

A = Anti-symmetriser

ai,j,k and bj,k variationally determined coefficients