MOLPRO

34 PROPERTIES AND EXPECTATION VALUES 262
34.4.2 Saving the NLMO orbitals (SAVE)
SAVE,record.file;
The NLMO orbitals are saved in the specified record, together with the NPA charges.
34.5 Finite field calculations
Dipole moments, quadrupole moments etc. and the corresponding polarizabilities can be obtained
as energy derivatives by the finite difference approximation. This is most easily done
with the DIP, QUAD, or FIELD commands. An error will result if the added perturbation is not
totally symmetric (symmetry 1). Note that the orbitals must be recomputed before performing
a correlation calculation.
34.5.1 Dipole fields (DIP)
DIP,xfield,yfield,zfield;
DIP+,xfield,yfield,zfield;
Add a finite dipole field to the one electron Hamiltonian and the core energy. The field strength
is given by xfield,yfield,zfield. DIP+ adds to any existing field, otherwise any previous field is
removed.
34.5.2 Quadrupole fields (QUAD)
QUAD,xxfield,yyfield,zzfield,xyfield,xzfield,yzfield;
QUAD+,xxfield,yyfield,zzfield,xyfield,xzfield,yzfield;
Exactly as the DIP command, but adds a quadrupole field.
34.5.3 General fields (FIELD)
FIELD,oper1,fac1, oper2,fac2, . . . ;
FIELD+,oper1,fac1, oper2,fac2, . . . ;
Adds one-electron operators oper1, oper2, . . . with the corresponding factors fac1, fac2, . . . to
the one-electron hamiltonian. The available operators are given in section 6.13. An error will
result if the added perturbation is not totally symmetric (symmetry 1).
FIELD+ adds to any existing field, otherwise any previous field is removed.
Note that FIELD does currently not modify core polarization potentials (CPP). If CPPs are
present, only DIP and QUAD should be used.
34.5.4 Examples
The first examples shows various possibilities to add perturbations to the one-electron hamiltonian.