Static and lattice vibrational energy differences between polymorphs

Jonas Nyman,Graeme M Day

doi:10.1039/c5ce00045a

Abstract

Lattice energy, entropy and free energy differences for over 500 pairs of known polymorphs are computed and discussed.

Highlights

Polymorphism, the possibility of a compound to exist in at least two different crystalline phases,[1] has important implications for the development of pharmaceuticals, organic semiconductors,[2] explosives and any other material where solid state properties must be controlled.[3]
3.1 Free energy convergence with phonon sampling The convergence of Helmholtz energy, entropy, zero point energy and heat capacity with respect to k-point sampling was studied to decide on a sampling density that gives sufficiently small errors in calculated thermodynamic quantities, while maintaning the computational efficiency required to evaluate properties of all 1061 crystal structures
Convergence of thermodynamic properties was investigated for a set of four polymorph pairs of theophylline (CSD refcode family BAPLOT), two polymorph pairs of maleic hydrazide (MALEHY) and the pair of 3,4-cyclobutylfuran (XULDUD) polymorphs (Fig. 1), chosen to represent crystal structures with varying types and strengths of intermolecular interactions

Summary

Introduction

Polymorphism, the possibility of a compound to exist in at least two different crystalline phases,[1] has important implications for the development of pharmaceuticals, organic semiconductors,[2] explosives and any other material where solid state properties must be controlled.[3] Unexpected polymorphism can have far-reaching economic and medical,[4,5] as well as legal[6] consequences. For these reasons, there is a strong motivation to develop our fundamental understanding of polymorphism, of property differences between polymorphs and, the ability to predict possible polymorphs a priori.

Methods

Results

Conclusion