From owner-chemistry@ccl.net Mon Aug 29 07:28:01 2011
From: "Rajagopala Reddy Seelam rajagopalaseelam-*-gmail.com" <owner-chemistry[-]server.ccl.net>
To: CCL
Subject: CCL: classification of MOs as sigma and pi orbitals reg
Message-Id: <-45352-110829070716-4406-mNYTzy0WLT3Vuacf3R6q4w[-]server.ccl.net>
X-Original-From: "Rajagopala Reddy Seelam" <rajagopalaseelam() gmail.com>
Date: Mon, 29 Aug 2011 07:07:12 -0400


Sent to CCL by: "Rajagopala Reddy Seelam" [rajagopalaseelam _ gmail.com]
Respected CCL Administrators and subscribers,

How can we classify a molecular orbital as sigma(sigma*), pi(pi*) and n(n*). If the basis set used in the abinitio calculation is small (like sto-3g and 3-21g) it is easy. But if we use large basis is task is not as straight forward as the previous one. Are there any rule of thumb available to classify a molecular orbital as sigma, pi etc. 

Can we use NBO analysis to get these. 

Please excuse me if my question is naive.