From owner-chemistry#* at *#ccl.net Mon May 11 12:59:00 2015
From: "Wirawan Purwanto wirawan0%yahoo.com" <owner-chemistry::server.ccl.net>
To: CCL
Subject: CCL: Making symmetry equivalence atomic orbitals
Message-Id: <-51367-150511125738-16626-VhNmGboHLN930wKmeW9Pfg::server.ccl.net>
X-Original-From: "Wirawan  Purwanto" <wirawan0::yahoo.com>
Date: Mon, 11 May 2015 12:57:37 -0400


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