*MP2 INPUT  

Purpose:

To direct MP2 calculation  .

.MP2 FROZEN  

Default = no frozen orbitals
READ (LUINP,*) (NFRMP2(I),I=1,NSYM)
Orbitals frozen in MP2 calculation

.PRINT  

READ (LUINP,*) IPRMP2
Print level for MP2 calculation

Comments:

The MP2 module expects canonical Hartree-Fock orbitals , the module will check the orbitals and exit if the Fock matrix has off-diagonal non-zero elements.

The MP2 calculation will produce the MP2 energy and the natural orbitals for the density matrix through second order. The primary purpose of this option is to generate good starting orbitals for CI or MCSCF, but may of course also be used to obtain the MP2 energy, perhaps with frozen core orbitals. For valence MCSCF calculations it is recommended that the ".MP2 FROZEN  " option is used in order to obtain the appropriate correlating orbitals   as start for an MCSCF calculation. As the commonly used basis sets do not contain correlating orbitals for the core orbitals and as the core correlation energy therefore becomes arbitrary, the ".MP2 FROZEN  " option can also be of benefit in MP2 energy calculations.