# [molpro-user] hexadecapole moment of CH4 using finite-field

Yurii Vlasov vlasov.yura at gmail.com
Wed Jun 9 11:09:11 BST 2010

```Dear Molpro Community,

I have a problem with the calculation of the hexadecapole moment of CH4
molecule using finite-field method. But I've got the value of Hexadec mom =
-2.01067478D+07 ! (It should be ~7 a.u. according to Maroulis, or if to
calculate the expectation value). May be I didn't understand correctly the
idea of finite field method...

Could anyone help me. I would be very appreciated

memory,20,m

GTHRESH, oneint=1.d-14, energy=1.d-9, step=1.d-5,
twoint=1.d-14, prefac=1.d-14
GTHRESH, coeff=1.0d-5, zero=1.0d-14
symmetry,nosym

geometry={
1 C1,,   0., 0., 0.,
2 H2,, 1.18912    1.18912    1.18912,
3 H3,, -1.18912   -1.18912    1.18912,
4 H4,, -1.18912    1.18912   -1.18912
5 H5,, 1.18912   -1.18912   -1.18912,
}
basis=avtz

f=[0.000001,-0.000001]
method=[hf]
k=0
do i=1,#f
field,zzzz,f(i)
hf
e(k)=energy
end do

k=0
n=1
do m=1,1
k=k+1
hexz(m)=(e(k)-e(k+n))/(f(1)-f(2))
end do

table,method,hexz