Support for MonteCarloAnisotropicBarostat?

[jchodera]

How would we add support to ThermodynamicState for MonteCarloAnisotropicBarostat? Can we just detect whether pressure is a scalar or vector, and handle the barostat appropriately?

[andrrizzi]

Yes, I think that would work.

[Olllom]

cross-referencing #437, where support for the MonteCarloMembraneBarostat and MonteCarloAnisotropicBarostat was added.

The membrane barostat is fully supported and lateral pressure can be controlled independently via the surface tension.

The anisotropic barostat is only supported if the pressure in all directions is the same. This covers the most common use case, where certain axes of the box are fixed.

I did not code up full anisotropic support for three reasons:

1. what would anybody use this for?
2. it adds significant complexity to the ThermodynamicState
3. not sure how the reduced potential would look like for anisotropic pressure.

[mrshirts]

not sure how the reduced potential would look like for anisotropic pressure.

This is something we are currently working on for GROMACS, but it may be a month or two before we've tested things and can share.