Ab initioprediction of the polymorph phase diagram for crystalline methanol

Abstract

Thermodynamic phase boundaries for three molecular crystal polymorphs are mapped out with ∼0.5 kJ mol–1 accuracy.

Overcoming the difficulties of predicting conformational polymorph energetics in molecular crystals via correlated wavefunction methods

“…96 The quasi-harmonic approximation is oen successfully used to approximate the volumedependent contributions to the phonons and lattice energies. 13,23,28,82,[91][92][93][94][97][98][99][100] Nevertheless, quasi-harmonic calculations remain considerably more expensive than purely harmonic calculations that neglect thermal expansion.…”

“…For the HMBI fragment calculations employing correlated wave function methods, large basis sets must be used to ensure convergence of the polymorph energetics, as demonstrated in ESI Section S1.2 † and many previous studies. 10,81,82,93,94,116,123,124 Here, MP2 and MP2D monomer and dimer energies at the complete-basis-set (CBS) limit were obtained using a development version of PSI4. 125 The correlation energy was extrapolated 126 to the complete-basis-set (CBS) limit using data from the aug-cc-pVTZ and aug-cc-pVQZ basis sets 127 and combined with HF/aug-cc-pVQZ.…”

“…Employing coupled cluster singles, doubles, and perturbative triples (CCSD(T)) in the context of a fragment method can give very reliable results, as demonstrated by quantitative prediction of the benzene lattice energy 81 or the prediction of the methanol polymorph phase diagram with $0.5 kJ mol À1 accuracy. 82 Unfortunately, even with fragment methods, CCSD(T) calculations are cost-prohibitive for crystals involving pharmaceutical-sized species. MP2 is more feasible computationally, but it suffers from well-known problems in the description of van der Waals interactions 83 that cause it to substantially overestimate the interaction energy in p-stacking complexes 84 and to over-bind the benzene crystal by $10-20%, 10 for example.…”

Is zeroth order crystal structure prediction (CSP_0) coming to maturity? What should we aim for in an ideal crystal structure prediction code?

“…The pharmaceutical industry would really welcome such a code, but currently the calculation of the phase diagram of crystalline methanol represents a major step forward in this regard. 3 The situation is more advanced for other materials, with a revision of the phase diagram of CaCO 3 over half the pressure range within the earth's mantle, 4 leading to the discovery of a new phase with implications for carbon storage in the deep mantle.…”

Control and prediction of the organic solid state: a challenge to theory and experiment

“…However, predicting the most stable polymorph requires modelling the free energy, rather than just the static lattice energy. This is a major computational challenge, as demonstrated by the recent calculation of the polymorph phase diagram of methanol [ 29 ]. Realistically including the differential effects of temperature on polymorphs is challenging as most organic crystals at ambient temperature are nearer to their melting points than 0 K, or decompose before melting.…”