UF₆: Numerical Frequencies, spin-orbit coupled ZORA

Sample directory: adf/Freq_UF6/

Calculation of spin-orbit coupled ZORA gradients for the LDA and GGA functionals is possible since the ADF2007.01 version.
Summary:

• Geometry optimization
• Frequencies with symmetric displacements
• Both for scalar relativistic ZORA and spin-orbit coupled ZORA

Geometry optimization

Here only the spin-orbit coupled input file for ADF is given (in the scalar relativistic case change "spinorbit" in "scalar"). The resulting TAPE21 is saved such that it can be used in the frequency calculation.

$ADFBIN/adf <<eor
Title  UF6 geometry optimization: scalar ZORA
integration 5 5
Geometry
 conv grad=1e-4
End
relativistic spinorbit zora
Basis
 Type TZP
end
ATOMS cartesian
1 U   .00000  .00000   .00000
2 F  2.00000  .00000   .00000
3 F -2.00000  .00000   .00000
4 F   .00000  2.0000   .00000
5 F   .00000 -2.0000   .00000
6 F   .00000   .0000  2.00000
7 F   .00000   .0000 -2.00000
END
end input
eor
mv TAPE21 UF6.t21

Frequencies with symmetric displacements

Computation of frequencies by symmetric displacements. The assumed equilibrium input structure should be given in Cartesian coordinates. The calculation starts with the optimized structure read from UF6.t21 (restart file). Again only the spin-orbit coupled input file for ADF is given.

The symmetry is determined automatically by the program as O(H), from the input coordinates. During the calculation first symmetric atomic displacements are constructed. The number of such displacements in each irreducible representation corresponds to the number of frequencies with the corresponding symmetry. All displaced geometries within one representation have the same symmetry, which enables us to use it to speed up the computation significantly. Another advantage of having the same symmetry is that the numerical integration data can be reused efficiently (see SMOOTH option) thus reducing the level of numerical noise in gradients and force constant matrix.

In case of spin-orbit coupling the frequencies can not (yet) be calculated with analytical second derivatives.

$ADFBIN/adf <<eor
Title  UF6 frequencies and IR intensities: spinorbit ZORA
Restart  UF6.t21
Geometry
  Frequencies Symm
End
integration 5 5
relativistic spinorbit zora
Fragments
 U t21.U
 F t21.F
end
ATOMS cartesian
1 U   .00000  .00000   .00000
2 F  2.00000  .00000   .00000
3 F -2.00000  .00000   .00000
4 F   .00000  2.0000   .00000
5 F   .00000 -2.0000   .00000
6 F   .00000   .0000  2.00000
7 F   .00000   .0000 -2.00000
END
end input
eor