Subject: Significant figures and single point calculations

From: Laurence Lavelle <[email-masked]>
Date: Thu, 20 May 1999 10:19:15 -0700

I was hoping that the various software companies that I contacted would
make an announcement to CCL. Since this has not occurred you should be
aware of the following.

Many software packages round off significant figures.

For example, an original file with Cartesian coordinates to 6 sig fig.

When saved as .pdb in HyperChem Professional 5 has 3 sig fig. 
When saved as Z-matrix, 4 sig fig. 

In Chem 3D ULTRA  5, bond lengths changed by 0.001 A. 
Again sig fig are different for different formats.

Babel 1.3 converted a 6 sig fig file to 3 sig fig when going from .hin to .pdb

Hopefully Gaussian will post significant figures for all file formats in
NewZMat. 

These round off errors will affect single point calculations. 

Laurence

""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
"""""""""""""""" 
Laurence Lavelle, Ph.D. 
University of California Los Angeles 
Department of Chemistry & Biochemistry and Molecular Biology Institute
Laboratory of Structural Biology & Molecular Medicine 
Los Angeles, CA 90095-1570, USA 

Email:[email-masked] 
Phone (Office): (310) 825-2083
Room 3048A Young Hall
Fax: (310) 206-4038  
Phone (Lab): (310) 206-8270
Room 269B MBI
http://www.doe-mbi.ucla.edu/people/lavelle/lavelle.html 
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
""""""""""""""""