Subject: CCL:G92/DFT bug? H and LYP -- Solution

From: [email-masked] (Gary Trucks)
Date: Fri, 3 Feb 95 20:53:57 EST

Thomas Fox wrote:
>>I was using the DFT module of Gaussian 92 (HP-PARisc-HPUX-G92/DFT-RevF.4)
>>and came across something that looks like a bug to me: when I try to
>>calculate an one-electron system (like the H atom) and use the Lee-Yang-Parr
>>functional, my G92 version stops with an IEEE division by zero error.

This problem was fixed some time ago (G92/DFT Rev.G); it does not affect
systems with more electrons. If you need this fix, contact Gaussian, Inc.,
and it will be sent to you at no charge.

Benny Johnson responded:
>There seems to be a lot of confusion in the literature over the definition
>of this method.  To my knowledge, there has never been a paper published in
>which the definition of the Becke3LYP method in G92/DFT has actually been
>given, nor does there seem to be any systematic validation study thoroughly
>documenting its performance.

This is not correct. Becke3LYP is specified completely and calibrated in
numerous papers and presentations.  Here are a few examples:

   P.J. Stephens, F.J. Devlin, M.J. Frisch and C.F. Chabalowski, 
   "Ab Initio Calculations of Vibrational Absorption and Circular 
   Dichroism Spectra Using SCF, MP2, and Density Functional Theory
   Force Fields," J. Phys. Chem. 98, 11623 (1994).

   Yue Qin and Ralph A. Wheeler, "Density-functional methods give 
   accurate vibrational frequencies and spin densities for phenoxyl
   radical," J. Chem. Phys. 102, 1689 (1995).

   Cary Chabalowski, "Current trends in Computational Chemistry"

   Phil Stephens, "Faraday Discussions"

   P.J. Stephens, F.J. Devlin, C.S. Ashvar, C.F. Chabalowski and 
   M.J. Frisch, "Theoretical Calculation of Vibrational Circular 
   Dichroism Spectra," Faraday Discucc. 99 (1994) in press.  
 
(Phil's work was also discussed in C&E News, January 16 (1995) 27.)

Johnson continues:
>I don't know if you're aware, but the method in G92/DFT is not a method of
>Becke's.  I have talked with Becke about this, and he is quite skeptical
>about the validity of using the particular LYP functional with his
>half-and-half approach employing his exchange functional.  So, you may want
>to reconsider whether this method is the one you actually want to use.

This confuses the Becke3LYP functional with Becke's half-and-half theory.
Becke3LYP is based on the suggestion by Becke of exact (i.e., Hartree-Fock)
exchange with local and gradient-corrected exchange and correlation terms
(A.D. Becke, "Density-functional thermochemistry III. The role of exact
exchange," J. Chem. Phys. 98, 5648 (1993)) and is *NOT* based on his half-
and-half theory (A.D. Becke, "A new mixing of Hartree-Fock and local density-
functional theories," J. Chem. Phys. 98, 1372 (1993)).

Sincerely,

Gary Trucks
Gaussian, Inc.