Re: [Towhee-users] VOLNPT output: an error message?

[Jure V. <jur...@ki...>]

Dear Marcus and Aric,

I have a related situation: I wish to simulate adsorption in a non-rigid 
crystal framework, which of course runs into the VOLNPT limitation.

> Indeed the error messages do mean there is a problem.  When you perform a
> volume move in Towhee it scales the center of mass position of all the
> molecules (in a manner appropriate for the volume change) and then keeps
> all of the intramolecular distances the same.  This is not possible when
> the "molecule" spans the periodic images with its bonding pattern.
> 
> You would need a completely different move that scaled the intramolecular
> distances for the volume change.  That would then lead to problems with any
> molecule that has a rigid bond length (as the attempt to change that bond
> length would result in an infinite energy) and also would be fairly
> inefficient as the intramolecular distances are quite sensitive.

I have been considering implementing this for towhee. Our material undergoes 
non-negligible changes in unit cell shape, so inefficiency is what we have to 
live with. Rigid bonds would remain forbidden, you can't have it both ways. 
Marcus, are you aware of any other limitations in towhee that I need to be 
aware of before I attempt this? Any advice?

Regards
Jure Varlec