CCL: Making symmetry equivalence atomic orbitals

 Sent to CCL by: Kirk Peterson [kipeters]=[wsu.edu]
 Dear Wirawan,
 yes, I believe you have the general understanding of the situation correct
 below.  If codes would use full atomic symmetry this presumably wouldn't be an
 issue, but generally you’re stuck with calculating one component of a
 degenerate atomic state in the highest abelian group, hence for example px will
 be ‘different’ than py or pz.
 I usually use the MCSCF program in Molpro for symmetry equivalencing. In this
 case you just state-average the various HF states corresponding to the different
 open shells. This is not a black-box procedure though.
 best,
 -Kirk
 > On May 11, 2015, at 9:57 AM, Wirawan Purwanto wirawan0%yahoo.com
 <owner-chemistry^ccl.net> wrote:
 >
 >
 > Sent to CCL by: "Wirawan  Purwanto" [wirawan0{}yahoo.com]
 > Hi,
 >
 > Can someone give me a pointer to how to make "symmetry
 equivalenced" orbitals? I am not that familiar with this terminology, and
 in some papers this is mentioned without any citation.
 >
 >
 > This is my limited understanding of it: in the context of Hartree-Fock
 calculation of an isolated atom (say, ROHF calculation of Co atom), the five 3d
 orbitals ended up not having the same shape and energy because of the
 symmetry-broken configuration (3d7 4s2). The symmetry equivalenced 3d orbitals
 would then be obtained by somehow restoring the degenerate nature of these
 orbitals (which would raise the variational energy by a little bit). I think
 this can also be done for e.g. diatomic molecule where the pix-piy degeneracy
 could be broken due to open shell nature of the HF solution.
 >
 >
 > Here are my questions:
 >
 > 1. Is this understanding correct?
 >
 > 2. What are the step-by-step way to make the symmetry equivalenced orbitals
 from the usual ROHF or UHF orbitals? Any reference or program that can do this
 from a MO output given by a quantum chemistry program (e.g. GAMESS,
 molpro...whatever you like), assuming that I know the composition of the
 underlying AO basis (i.e. which function is 1s, ...2px,... 3dxy, and so on).
 >
 >
 > Thanks,
 > Wirawan>      https://urldefense.proofpoint.com/v1/url?u=http-:-//www.ccl.net/cgi-bin/ccl/send_ccl_message&k=EWEYHnIvm0nsSxnW5y9VIw%3D%3D%0A&r=ndj2Vta%2FisUMMOFOMobgvg%3D%3D%0A&m=MoY4K2vo2Vt6auAeG3H1BHQ%2BbZg6M4vlbxitj1iUZPo%3D%0A&s=54de310d7862582eda966c6d2c71d66bde1c6e3fea01c4f40b19982b538b7872>;
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