From owner-chemistry@ccl.net Sat Oct  2 01:33:00 2010
From: "Raj Thakur Veer meandme_meandme2003%x%yahoo.com" <owner-chemistry^server.ccl.net>
To: CCL
Subject: CCL:G: clatharte (calc of deltah and deltag; Should I use readisotope option)
Message-Id: <-42884-101002013135-24634-4Rv8/p1PN7vBl3MeU3w+/A^server.ccl.net>
X-Original-From: "Raj  Thakur Veer" <meandme_meandme2003=yahoo.com>
Date: Sat, 2 Oct 2010 01:31:34 -0400


Sent to CCL by: "Raj  Thakur Veer" [meandme_meandme2003!=!yahoo.com]
Dear CCLers, In a system of clathrate having an entraped guest-gas atom (20 water molecules and 1 noble gas atom in its cage), is this the way to calculate deltaH and deltaG from Gaussian 09 Therochemistry output.
deltaH= [Eo+Hcorr (of whole system)] - [Eo+Hcorr (of 20 water molec) + Eo+Hcorr (of guest atom)]

Similarly deltaG would be calculated as;

deltaG= [Eo+Gcorr (of whole system)] - [Eo+Gcorr (of 20 waer molec) + Eo+Gcorr (of guest atom)]

Secondly, in order to calculate thermochemical data at a different temperature then default (298.15 k and 1 atm) in gaussian 09, should I use the readisotope option in gaussian 09 to use my exp. temp and pressure or I can just use freqchk command to extract data at different temp and pressures from checkpoint file I have saved from calculations which originally were done at default gaussian temp of 298k and 1 atm.for instance, if I want to extract data at 0k, 100k and 150k (or else) and 1000 atm. should I use freqchk command in gaussian to extract data  at this specific temp and pressure or should i rerun gaussian calc and use readisotope option to specify my exp. temp and pressure. BUt again, should i have to rerun new calc for every temp. and pressure value. I appreciate your help.

~Titan