Subject: Mixing basis sets?

From: Josh Bowden <[email-masked]>
Date: Wed, 08 Jul 1998 13:51:21 +0930

Hello all,

As a continuation of recent discussion on this list about 3-21G vs 6-31G*, can I ask if anyone 
has information on mixing basis sets in a calculation. Programs such as CRYSTAL 95 and 
HyperChem (probably others as well) allow you to apply different basis to individual atoms. If the lack of polarization functions ( as stated by [email-masked]) is a problem can you not apply a bigger basis set to 'problem' atoms and reduce the basis of others?
Has anyone looked at this systematically and is there any referencs on this topic?
Are there any problems in this metholodgy (does it have any major downfalls)?

Thankyou for your time, I will return a summary.

Josh Bowden (hoping this is not a stupid question!)
Ian Wark Research Institute
University of South Australia
E-mail : [email-masked]