Subject: Calculate Heat of formation by Guassian98

From: Hu LiHong <[email-masked]>
Date: Thu, 2 Jan 2003 13:09:43 +0800 (HKT)

Hello all,

Happy new year!

I'd like to use Guassian to calculate the heat of formation of some 
compounds. I am using DFT method and basis set 6-311G(d,p) to optimize 
the structures and calculate the frequency. After checking the website of 
www.gaussion.com, I used the formula for calculating the enthalpy of 
formation, it is a little complicated but I found the result of enthalpy 
of formation have large difference from experimental values. I don't know 
what's wrong with it? 

Who can tell me 1) whether I can use the formula in the website 
                2) what should be noticed when I am using it
                3) if there is other easier method to calculate the 
                   enthalpy of formation by using the energy calculated by 
                   Guassian 98?

I'll appreciate you very much

Cheer,

Yours,

Carol