MOLPRO

34 PROPERTIES AND EXPECTATION VALUES 264
***,H2O finite field calculations
r=1.85,theta=104
!set geometry parameters
geometry={O;
!z-matrix input
H1,O,r;
H2,O,r,H1,theta}
basis=avtz
!define default basis
field=[0,0.005,-0.005]
!define finite field strengths
$method=[hf,mp4,ccsd(t),casscf,mrci]
k=0
do i=1,#field
dip,,,field(i)
do m=1,#method
k=k+1
$method(m)
e(k)=energy
enddo
enddo
!loop over fields
!add finite field to H
!loop over methods
!calculate energy
!save energy
k=0
n=#method
do m=1,#method
k=k+1
energ(m)=e(k)
dipmz(m)=(e(k+n)-e(k+2*n))/(field(2)-field(3)) !dipole moment as first energy derivative
dpolz(m)=(e(k+n)+e(k+2*n)-2*e(k))/((field(2)-field(1))*(field(3)-field(1))) !polarizability
enddo
table,method,energ,dipmz,dpolz
title,results for H2O, r=$R, theta=$theta, basis=$basis
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http://www.molpro.net/info/current/examples/h2o_field.com
34.6 Relativistic corrections
Relativistic corrections may be calculated within the Cowan-Griffin approach by computing expectation
values of the mass-velocity and 1-electron Darwin integrals; these should be generated
using the property integral program with keyword REL The expectation values can be computed
within the SCF, MCSCF and CI programs in the usual way using the EXPECT command, again
with the keyword REL. The mass-velocity and Darwin terms, and their sum are subsequently
available through the MOLPRO variables MASSV, DARW and EREL respectively.