Geometric Modeling in the Prediction of Molecular Crystal Structures: The Close-Packing Principle Revisited.

7^th October 2024, 14:00
Miloslav Torda
MIF

Abstract

A. I. Kitaigorodsky’s Close-Packing Principle states that “the mutual arrangement of the molecules in a crystal is always such that the ‘projections’ of one molecule fit into the ‘hollows’ of adjacent molecules,” highlighting the underlying geometries of molecular interactions in crystalline ground states. We revisit this principle to demonstrate that a geometric approach can substantially reduce the computational effort required to predict stable phases of molecular crystals. By leveraging the duality between interaction energy and packing density through geometry-informed programming, we generate first-approximation structures during the initial stages of Crystal Structure Prediction (CSP) within minutes on a standard laptop. Focusing on close packings of volumetric molecular models—where interactions are predominantly van der Waals forces without significant charges or electron exchange—we apply this purely geometric method to various rigid organic molecules. Our results show that integrating the Close-Packing Principle as an inductive bias in CSP workflows significantly reduces computational complexity, leading to more efficient and accurate predictions of molecular crystals.