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Quantum monte carlo methods in biologocal chemistry

Posted: Mon Oct 07, 2013 9:09 am
by Jhalak
Are quantum monte carlo methods are developed to the extent of exploring the problems in biological chemistry? In particular I am interested to know their possible uses in the study of protein behaviour and their inter- and intra-molecular behavior. Can we study these problems using any available QMC code/ tool?

Re: Quantum monte carlo methods in biologocal chemistry

Posted: Wed Oct 09, 2013 11:55 am
by Mike Towler
Dear Jhalak,

Whether the problem is biological or otherwise is irrelevant. If it's a question of atoms banging into each other and you're not studying consciousness, it's just chemistry as far as we're concerned! Then, as with other methods such as DFT, the only issues are whether the problem can be reduced to involve a number of atoms (particles) that the software/hardware combination can cope with, and whether it involves time scales or length scales that are too long. Remember also that the ability of CASINO to do 'molecular dynamics' type calculations is extremely limited and in that case people really need to study e.g. vibrating diatomic molecules with QMC before being let loose on bigger more interesting dynamical problems.

If your atoms have low atomic numbers and you have a very big computer, you could conceivably treat a problem with a couple of thousand electrons with CASINO, either as a finite system, or per cell in an artificially periodic system. And yes, that includes bits of proteins.

QMC does have the distinct advantage (unlike DFT) that it gets weak interactions such as hydrogen bonding and van der Waals right, and this is likely to be important in understanding intermolecular interactions in biological systems.