Recap on Basis Sets

Pablo OrdejonICMAB-CSIC

Basis Sets in SIESTA

• Generated from the solution of the FREE ATOM (with the pseudopotential)

• Finite range: (r) = 0 for rrc (boundary condition)

• Energy shift by confinement: shorter rc means higher energy E

Single- (SZ)and

First- in MZ bases

Shape of the orbitals: rc

O 2s orbital

rc = 3 a.u.

E = 500 meV

rc = 4.5 a.u.

E = 10 meV

Shape of the orbitals: rc

Fe 3d orbital

Fe 4s orbital

rc = 6 a.u.

E = 400 meV

rc = 10 a.u.

E = 5 meV

Energy vs. rc - Molecules

H2O

Energy vs. rc - Solids

Bulk Fe

Second- in DZ bases

Split Valence

Gaussians

SZ

DZ

Split Valence

SIESTA

SZ

DZ

Shape of the orbitals: DZ

O 2s orbital

E = 10 meV

SplitNorm 0.15

Shape of the orbitals: DZ

O 2s orbital

E = 500 meV

SplitNorm 0.15