ELSEVIER SPECTROCHIMICA ACTA PART A Spectrochimica Acta Part A 53 (1997) 1325-1340 Quantum chemistry based force fields for soft matter Matthew A. Glaser a,*, Noel A. Clark a, Edgardo Garcia b, David M. Walba c ’ Condensed Matter Laboratory, Department of Physics, University of Colorado, Boulder, CO 80309, USA b Department of Chemistry, University of Brazilia, Brazilia, Brazil ’ Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA Received 16 December 1996; received in revised form 23 January 1997 Abstract We describethe use of ab initio electronic structure calculations in the development of high-quality classical interaction potentialsfor liquid crystal modeling.Our focusis on methods for the rapid, on-demand creation of force fields for use in mean field theory basedcalculations of materials properties, employed for routine pre-synthesis evaluation of novel liquid crystalline materials.The role of quantum chemistryin the development of intermolecular interaction potentials for large-scale simulations of soft matter is also discussed, and directions for future work are outlined. The utility of quantum chemistry derived force fields for liquid crystal modeling is illustrated by two exampleapplications:mean field theory based prediction of the spontaneous polarization density P of ferroelectric liquid crystals, and large-scale simulation studies of the nanosegregation af polymer precursorsin smecticliquid crystal hosts. 0 1997Elsevier Science B.V. Keywords: Liquid crystal; Modeling; Force fields; Quantum chemistry 1. Introduction Liquid crystals (LCs), broadly defined as states of matter having order intermediate between that of crystalline solids and isotropic liquids, exemplify the wide range of possible modes of self-organiza- tion inherent in organic matter. Much of the current interest in LCs stems from the variety of distinct types of order exhibited by these materials (over 20 different thermotropic LC phases are known). Understanding the molecular basis for the rich phase behavior of liquid crystalline materials * Corresponding author. Tel: + 1 303 4927543; fax: + 1 303 4922998; e-mail: glaser@bly.colorado.edu. represents one of the most fundamental challenges in soft condensed matter physics, and is an essen- tial prerequisite to the effective exercise of chemical control over LC properties. The self-organizing tendency and fluidity of LCs lend them unique properties that are utilized by biological systems (e.g. in lipid bilayers) and that enable their use in a variety of applications, most notably for electro- optics (e.g. in display technology). Our current research focuses on the improvement of basic understanding of the molecular ordering and re- sulting macroscopic behavior of liquid crystals, and the development of novel chiral LC materials, particularly ferroelectric liquid crystals (FLCs), for electro-optical and nonlinear-optical applications. 1386-1425/97/$17.00 Q 1997 Elsevier Science B.V. All rights reserved. PI1 SO584-8539(97)00034-2