From owner-chemistry #at# ccl.net Mon Oct  4 01:52:00 2010
From: "Gkourmpis, Thomas Thomas.Gkourmpis+*+borealisgroup.com" <owner-chemistry[a]server.ccl.net>
To: CCL
Subject: CCL:G: clatharte (calc of deltah and deltag; Should I use readisotope option)
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Date: Mon, 4 Oct 2010 07:50:17 +0200
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Sent to CCL by: "Gkourmpis, Thomas" [Thomas.Gkourmpis^^borealisgroup.com]
Thakur Hi

With respect to your second question I would use the freqchk routine and read the checkpoint file. The only thing you need is a well optimised structure and the relevant checkpoint file. The input line should look something like this

%chk=mychk
# Freq=(ReadFC,Temperature=value,Pressure=value) Geom=AllCheck

This way you can run every combination of pressure and temperature you want.

I hope this helps

Thomas

-----Original Message-----
> From: owner-chemistry+thomas.gkourmpis==borealisgroup.com(0)ccl.net [mailto:owner-chemistry+thomas.gkourmpis==borealisgroup.com(0)ccl.net] On Behalf Of Raj Thakur Veer meandme_meandme2003%x%yahoo.com
Sent: Saturday, October 02, 2010 7:32 AM
To: Gkourmpis, Thomas
Subject: CCL:G: clatharte (calc of deltah and deltag; Should I use readisotope option)


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.

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