SCM: Examples

Relativistic effects: Platinum slab

Sample directory: band/e_Pt_slab/

This example can of course be compared directly to the Cu slab. This example is important, as SCF convergence is frequently difficult in slab calculations. The specifications in the CONVERGENCE, SCF, and DIIS blocks are typical. Such settings are recommended in slab calculations with convergence problems.

The DEGENERATE subkey specifies that bands with the same energy should have the same occupation numbers. This helps SCF convergence. The same is true for the values for the MIXING subkey in the SCF block and the DIMIX subkey in the DIIS block. Please note that the recommended value for Mixing is approximately half of the value for Dimix.

Another important feature in BAND is that it enables relativistic treatments for heavy nuclei. Both the ZORA scalar relativistic option and spin-orbit effects have been implemented. The line

Relativistic ZORA SPIN

specifies that in this case both the scalar relativistic effects (ZORA) and spin-orbit effects (SPIN) will be taken into account. Whereas the ZORA keyword does not make the calculation much more time-consuming, the same cannot be said for the spin-orbit option. Usually the ZORA keyword will give the most pronounced relativistic effects and the spin-orbit effects will be a fairly minor correction to that. We therefore recommend scalar ZORA as a good default method for treating heavy nuclei.

The DEPENDENCY keyword means that the calculation should continue even if the basis is nearly linearly dependent (as measured by the eigenvalues of the overlap matrix).

$ADFBIN/band << eor
Title Platinum slab

Comment
 Technical
   Low quadratic K space integration
   Low real space integration accuracy
 Features
   Lattice   : 2D
   Unit cell : 3 atoms, 1x1
   Basis     : NO+STO w/ core
   Options   : Spinorbit ZORA
End

Convergence
  Degenerate 1.0E-03
End

SCF
 Iterations 60
 Mixing 0.06
End

DIIS
 NCycleDamp 15
 DiMix 0.15
End

KSpace 3
Accuracy 3

Relativistic ZORA SPIN

Dependency Basis=1E-8

Define
latt=7.41
lvec=latt/SQRT(2.0)
ysh=lvec/SQRT(3.0)
dlay=latt/SQRT(3.0)
End

Lattice
 SQRT(3.0)*lvec/2.0  0.5*lvec
 SQRT(3.0)*lvec/2.0 -0.5*lvec
End

Atoms Pt 
  0   0        0    :: layer 1
 -ysh 0.0     -dlay :: layer 2
  ysh 0.0 -2.0*dlay :: layer 3
End

...

END INPUT
eor

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