Subject: G92 - order of atoms in the input

From: [email-masked] (Michael Shephard)
Date: Thu, 4 May 95 13:04:01 PDT

--
I thought I would draw this to the attention of the CCL subscribers
and invite any explanation of this problem encountered (and solved)
with G92/DFT

A HF/3-21G single point calc on a large system (132 atoms, 93 heavies)
The calculation was done in cartesian coordinates. 
Route card: #P HF/3-21G GEOM=COORD SCF=(DIRECT, TIGHT)

Now, running this calculation with my initial input file, where
the Hydrogens and Heavies were listed in no particular order
resulted in a failure of the calculation:

 >  Leave Link  303 at Fri Apr 21 00:47:53 1995, MaxMem=7000000 cpu:157.6
 >  (Enter /usr/local/g92/l401.exe)
 >  PROJECTED INDO GUESS.
 >  Unable to orthonormalize alpha MO coefficients.
 >  Error termination in Lnk1e.
 > Segmentation fault

I then reordered the atoms in the input file so as to place all
heavy atoms first. The calculation now proceeded without trouble,
(as did a repeat of this calculation with all heavy atoms reordered to
place them at the end of the input).

Oddly enough, a similar calculations, involving a different conformers
of this system, was successful using an "unordered" input
file. These successful input files only had a very slightly different
order of heavies and hydrogens compared to the failed input.

Any ideas as to why this happened?

_________________________________________________________________________
| Michael Shephard.                  |      [email-masked]      |
| University of New South Wales.     |  [email-masked]  |
| Australia                          |                                  |