[gmx-users] Re: Calculating lattice enegies for molecular crystals

[David van der Spoel]

On 2011-01-10 15.40, Adam Bin Idu Jion wrote:
> Hi!
> How do you calculate the lattice energies for molecular crystals?
> For example, I have a system of alpha-glycine crystals (for example, a
> slab of 420 crystalline molecules).
> Each unit cell has 4 glycine molecules.
> How do I calculate its lattice energy (i.e. the energy to bring the
> molecules from infinity into the lattice)?
> Should I include the LJ(SR) and Coulomb(SR) terms?
> Regards,
> Adam
>
Same as vaporization enthalpy from a liquid
DH = kT + Epot(g) - Epot(crystal)

so you have to compute the energy in the gas phase as well. You want to 
compute this using a SD integrator to avoid the flying ice cube effect 
while still allowing intramolecular conformational changes.

Good luck.
-- 
David van der Spoel, Ph.D., Professor of Biology
Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:	+46184714205.
spoel at xray.bmc.uu.se    http://folding.bmc.uu.se