(136c) Capturing the Role of Temperature and the Sensitivity to Energy Function Complexity in Crystal Polymorph Stability Using Molecular Modeling
AIChE Annual Meeting
2017
2017 Annual Meeting
Pharmaceutical Discovery, Development and Manufacturing Forum
Computational Solid State Pharmaceutics
Monday, October 30, 2017 - 1:12pm to 1:33pm
Twelve small molecule organic systems with known temperature-mediated transformations were modeled with the point-charge OPLS-AA potential. Our simulations correctly identify the high temperature solid form as having a larger entropy than the low temperature form in all systems examined. The estimated entropy differences in the classical point-charge potential are significantly closer to experimental measurements than estimated enthalpy differences. This result suggests that entropy difference estimates are less sensitive to the complexity of the simulation potential than the corresponding enthalpy estimates.
We further probe the energy function sensitivity by directly computing the added effects of a more accurate polarizable Hamiltonian on polymorph free energies. We show that the change in free energy to the more complex potential comes predominately from enthalpic rather than entropic contributions in the system examined.