[Wien] RMT choice and cell size

[Chandrika]

Hello Wien Users,
In doing volume optimisations I found that derived cell dimensions are very sensitive to RMT. For example when I optimised the structure of a cubic SiC with RMT 1.8 I get optimised a,b,c ~ 4.1 A. When I reduced RMT to 1.4, I get optimised a, b, c ~3.6 A. This is a large change.
My question is how small should one go with RMT reduction? How much smaller than the covalent radius can RMT go (Si = 1.1 A)? Do I keep reducing it till I get the lowest energy crystal size? I am interested in deriving total energy and cell diemnsions.
I have read the Optimisation Notes  by Marks (highly useful) and the FAQ by Blaha but perhaps I have missed a point.
Please suggest.
Thank you in anticipation.
Chandrika

-----------------------------------------------------------------------------------------
Dr (Ms) Chandrika Varadachari
Raman Centre for Applied and Interdisciplinary Sciences
16A Jheel Road
Calcutta 700075
India
Tel : 91-33-24830029
Fax : 91-33-24180610
web : www.rcais.org.in
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20060318/d6755d55/attachment.html