[molpro-user] {SPAM}? how to get correct symmetry

[Gerald Knizia]

On Monday 14 February 2011 07:54, Yulia Kalugina wrote:
> Could you advise me how to solve the problem: I need to get D2h symmetry
> for porphine, however, with the card SYMMETRY, X, Y, Z it doesn't work. I'm
> sure, that input corresponds to D2h symmetry.

The problem is the running index you specified your geometry in z-matrix 
format:
 1,H1,,      1.100886617         0.000000000         0.000000000
 2,H2,,     -1.100886617         0.000000000         0.000000000
 3,N1,,      0.000000000        -2.034073735         0.000000000
 4,N2,,      0.000000000         2.034073735         0.000000000
 5,N3,,      2.113013996         0.000000000         0.000000000
 6,N4,,     -2.113013996         0.000000000         0.000000000
etc. The first number before the chemical symbols, (e.g., the "3," in "3,N1,,
[...]") for which in your input you have a different one for each atom, is 
interpreted as "group number". This group number is used to distinguish 
*different* kinds of atoms of the same element (see 
https://www.molpro.net/info/alpha/doc/manual/node99.html). For example, you 
can assign a different basis set to each different group. Or in this case, 
you could assign a different basis set to each different atom, thus breaking 
the symmetry. You don't actually do that later on, but you could, and this is 
enough for the symmetry detection to identify this molecule as having no X or 
Y symmetries.

The solution is to remove the numbers before the chemical symbols. E.g., turn
 1,H1,,      1.100886617         0.000000000         0.000000000
 2,H2,,     -1.100886617         0.000000000         0.000000000
into
 H1,,      1.100886617         0.000000000         0.000000000
 H2,,     -1.100886617         0.000000000         0.000000000
-- 
Gerald Knizia