[molpro-user] A question about second moment in molpro

[Cong Wang]

Dear everyone,

 Hello,

 Excuse me, I have a question of the definition of second moment in
molpro. From the manual

http://www.molpro.net/info/current/doc/manual/node68.html#sec:gexpec
SM      1       XX, YY, ZZ, XY, XZ, YZ  second moments

Seems the diagonal element is a positive definite quantity, while the
example on water molecule is negative

http://www.molpro.net/info/current/doc/manual/node69.html
 METHODS     DIP           SMXX          SMYY          SMZZ
 HF        0.82747571   -5.30079792   -3.01408114   -4.20611391

Does the SM mean \sum_I Z_I R_I^2 - \sum_i r_i^2  or  (\sum_I Z_I R_I
- \sum_i r_i)^2 that counts both nuclei and electron?

Thank you very much
Best regards
Cong Wang

Ph. D. Student
Department of Chemistry
Laboratory for Instruction in Swedish
University of Helsinki
A.I. Virtanens plats 1
P.O. Box 55
FI-00014 University of Helsinki
FINLAND