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** read the RHF orbitals in Gamess and identify those who could be good guess orbitals for : 1s core of F, 2s lone pair, 2px lone pairs,... active orbitals
 
** read the RHF orbitals in Gamess and identify those who could be good guess orbitals for : 1s core of F, 2s lone pair, 2px lone pairs,... active orbitals
 
** then build the ''$gus'' section in XMVB input accordingly, and start your calculation (don't forget to add again ''vbtyp=xmvb'' in the $control section of Gamess input)  
 
** then build the ''$gus'' section in XMVB input accordingly, and start your calculation (don't forget to add again ''vbtyp=xmvb'' in the $control section of Gamess input)  
 +
* For the VBCISD calculation on F<sub>2</sub> you should add ''NCOR=2'' in the ''$ctrl'' section, as there is two core orbitals (core of each fluorine) to freeze in the calculation
 
* To compute the bond energy at the BOVB level, you can simply use the ROHF energies computed with Gamess for the separate fragments (F atoms here), because the L- and D-BOVB wave functions (like the VBSCF one) dissociate to uncorrelated separate fragments.
 
* To compute the bond energy at the BOVB level, you can simply use the ROHF energies computed with Gamess for the separate fragments (F atoms here), because the L- and D-BOVB wave functions (like the VBSCF one) dissociate to uncorrelated separate fragments.
 
* To compute the bond energy at the VBCISD level, you should however compute the separate fragments at this level of theory.
 
* To compute the bond energy at the VBCISD level, you should however compute the separate fragments at this level of theory.

Version du 10 juillet 2012 à 08:14

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Basics of VB theory and XMVB program