[gmx-users] QMMM free energy

Robert fiske rfiske_ at hotmail.com
Wed May 30 18:00:29 CEST 2007

>I'm not a QM expert myself (Gerrit, comments?),  but I'm pretty sure  the 
>main reason is that you cannot either mutate atom types or  decouple 
>interactions gradually in the QM part of the system. Once  this is solved 
>for a pure QM system it should be straightforward to  implement the QM/MM 
>interface of it.

One of the main things we plan to do with the free energy code (once I can 
confirm I'm doing things right) is to modify the charge of the quantum 
system for the lambda values, so atom types don't need to be modified for 
this I believe, although I see how that could complicate other types of free 
energy calculations.  As for decoupling interactions I don't know what 
impact that has for changing of charge.

For now, are there any major complications if all we want to do is modify 
the charge from state A to state B (assuming the interaction problems you 
mentioned aren't a problem)


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