Subject: Ab Initio calculations on SiO2

From: "John P. Kaszuba" <[email-masked]>
Date: Sat, 18 Jan 1997 09:57:47 -0700 (MST)

List Members,

We are using CRYSTAL92 to look at SiO2 polymorphs.  For alpha quartz we 
calculate a minimum energy at a unit cell volume that is larger than it 
should be.  We are using 3-21G* on Si and 6-21G* on oxygen.  Although we 
are increasing the sophistication of our basis set on Si, I can't help 
but wonder if the error is tied into a problem with electron 
correlation.  

Also, I read in the archives from the past few months about the 0.893 scale 
factor for frequency calculations.  Corrections were applied to the final 
calculated frequencies.  I figure our problem is related.  But I'm 
thinking in our case it would be appropriate to fiddle with the "Pople scale 
factor" that is a part of the basis set input.

Any comments or suggestions?

Thank you

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John P. Kaszuba
Department of Geology and Geological Engineering
Colorado School of Mines
Golden, Colorado  80401

phone: (303) 273-3066
fax:  (303) 273-3859
email:  [email-masked]
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