CamCASP/BasisSets

CamCASP => Basis Sets

Issues

Fifth Row Atoms

It isn't clear which basis sets should be used for these atoms. They are heavy atoms and we face two difficulties:

1. Too many electrons
2. Relativistic effects are important

Both can be resolved using effective core potentials (pseudo potentials), but it still isn't clear to me how CamCASP needs to be changed to handle such potentials.

For the present, perhaps we should allow such calculations using all electrons. From the EMSL Basis Library the following basis sets seem appropriate:

• Main Bases
  • def2-SVPD : Split-Valence basis set + Polarization + Diffuse basis functions
  • def2-TZVPD : Triple-Zeta-Valence basis set + Polarization + Diffuse basis functions
  • def2-TZVPPD : Triple-Zeta-Valence basis set + Two Sets of Polarization + Diffuse basis functions
  • Sadlej VTZ2P Valence Triple zeta + Polarization on All Atoms
• Auxiliary Bases
  • cc-pVXZ-PP-RI, X = D,T,Q,5 : auxiliary basis sets for for second-order correlation methods using the resolution-of-the-identity approximation for electron repulsion integrals.(RI-MP2, RI-CC2, RI-CIS(D), RI-ADC(2),...) From Christof Hattig. But these look like they have been tailored for the equivalent ECP basis sets.
  • aug-cc-pVTZ-PP-RI Diffuse : Diffuse functions for above. Same restriction as above.
  • Turbomole basis sets - don't seem to be many of these.

Well, it isn't clear to me which of these bases can be used. I could try the Sadlej/aug-cc-pVTZ-PP-RI combination and see what we get. But this is far from ideal.