Subject: The meaning of "SGG" and the use of "PW91" in G98W

From: "TELKUNI" <[email-masked]>
Date: Thu, 24 May 2001 00:49:50 +0900

Hello, Dear CCLers

I am a novice user of Gaussian(G98W RevA.7) and have two questions of it.
Any answers, I will appreciate (including additional advice.)

1)
  I had set the Route Section to calculate CO2 as "# BLYP/6-31G(d) Pop=Reg
Test",
I got the "Initial guess orbital symmetries" as follows:

       Occupied  (SGG) (SGG) (SGU) (SGG) (SGU) (PIU) (PIU) (SGG)
                 (SGU) (PIG) (PIG)
       Virtual   (PIU) (PIU) (SGG) (SGU) (SGG) (?A) (?A) (SGG)
                 (SGG) (SGG) (SGG) (SGG) (DLTG) (?A) (DLTG) (PIG)
                 (PIG) (PIG) (PIG) (PIG) (PIG) (DLTU) (SGU) (SGU)
                 (SGU) (SGU) (SGU) (DLTU) (PIU) (PIU) (PIU) (PIU)
                 (PIU) (PIU)

   I don't know the true meaning of these strings PIU, SGG.  With the words
"orbital symmetries",  I think "PIU" means PI(pi, it's a Greek alphabet) orbital
has the "U" type symmetry, and "SGU" means that SG(sigma, also Greek
alphabet) has the "U" type symmetry.

  Is my guess correct? ... I am wondering because I can't explain "DLTU" by my
guess.

2)
  In the G98 User's Reference_2ndEdition, it is written that PW91 has two
meanings:
 1st) Perdew and Wang's 1991 gradient-corrected correlation functional,
 2nd) The Exchange component of Perdew and Wang's 1991functional.

  When I use the key word PW91, for example with the bias 6-31G(d) to calculate
the structure, should I write PW91/6-31G(d) or PW91PW91/6-31G(d) in the
Route Section?

  I will summarize the answers for novice users of G98, just like me!

  Thanks in advance

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       Telkuni Tsuru     [email-masked]