Crystal formation and stability: Physical principles and molecular simulation

Abstract

The physical principles of chemical bonding are reviewed in the Feynman perspective. The Coulomb-London-Pauli model, which separates intermolecular interaction into Coulombic, dispersion and repulsion terms, is reviewed and its incorporation into empirical or semi-empirical force fields is described in comparison with ab initio quantum chemical computation. Quantitative assessments of pair-wise intermolecular coupling energies are presented, and orders of magnitude are established for several types of crystal construction. The wide energetic separation between dispersive and ionic aggregation is quantitatively evaluated. Molecular dynamics (MD) and Monte Carlo (MC) simulation techniques are succinctly described. Key problems in molecular-level pictures of crystal nucleation and growth are outlined, and possible applications of evolutionary (MC or MD) simulation are introduced and discussed. More generally, the significance and value of molecular simulation is criticized. A final section deals with the related phenomenon of crystal polymorphism, with its underpinnings in the kinetics of nucleation versus thermodynamics of crystal stability. The physical principles of chemical bonding are reviewed in the Feynman perspective. The Coulomb-London-Pauli model, which separates intermolecular interaction into Coulombic, dispersion and repulsion terms, is reviewed and its incorporation into empirical or semi-empirical force fields is described in comparison with ab initio quantum chemical computation. Quantitative assessments of pair-wise intermolecular coupling energies are presented, and orders of magnitude are established for several types of crystal construction. The wide energetic separation between dispersive and ionic aggregation is quantitatively evaluated. Molecular dynamics (MD) and Monte Carlo (MC) simulation techniques are succinctly described. Key problems in molecular-level pictures of crystal nucleation and growth are outlined, and possible applications of evolutionary (MC or MD) simulation are introduced and discussed. More generally, the significance and value of molecular simulation is criticized. A final section deals with the related phenomenon of crystal polymorphism, with its underpinnings in the kinetics of nucleation versus thermodynamics of crystal stability. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.