### UB Distinguished Professor of Chemical Engineering, University of Buffalo

## Big Properties from Small Simulations

##### Friday, January 29, 9:30 AM

##### 1175 Benedum

**ABSTRACT:** Much of the momentum in molecular simulation is toward the simulation of bigger systems and longer time scales. This trend is a natural outgrowth of the sustained advances in computing speeds over recent decades, as well as improvements in algorithms. But are there ways to extract big-system behavior by looking carefully at how small clusters of molecules interact? For equilibrium phenomena at least, there are indeed well established formalisms to do just that. Moreover, recent advances in simulation methods can be transferred to these treatments to make them more broadly usable.

A prime example is found in the virial equation of state, which provides the standard treatment for the gas phase. Difficulty in computing the virial coefficients has left its mathematical behavior and general utility largely unexplored. Can it, for example, be used to provide a general location for the critical point? What is its convergence behavior when applied to realistic systems? Mixture properties are treated exactly in the virial equation, so what can we learn about mixture behavior from it? We show how methods for computation of the free energy by molecular simulation can be used to calculate virial coefficients, and with this capability we address some of the questions raised above. Each simulation is small, involving fewer than ten molecules, yet in some cases with the virial approach these simulations can describe bulk behavior more accurately than traditional simulations of 10,000 molecules! We further discuss extensions of the virial treatment and show that these ideas can significantly expand its range of application.

**BIOGRAPHY:** *David Kofke received his B.S. in chemical engineering in 1983 from Carnegie-Mellon University, and his Ph.D. in 1988 from the University of Pennsylvania, where he worked under the supervision of Eduardo Glandt. Since 1989 he has been on the chemical engineering faculty of the University at Buffalo (SUNY), where he now holds the rank of UB Distinguished Professor and is Department Chair. Prof. Kofke’s expertise is in molecular simulation. His research interests consider the development and understanding of molecular simulation methods, particularly as they pertain to free-energy calculations and configurational integrals in general.*

*Author of nearly 100 refereed publications, Prof. Kofke received a Presidential Young Investigator Award in 1990, the SUNY Chancellor’s Award for Excellence in Teaching in 1994, and in Research and Creative Activity in 2004; he is the 2004 recipient of the triennial John M. Prausnitz Award for applied chemical thermodynamics, and in 2007 he was awarded the Jacob F. Schoellkopf Medal from the Western New York Section of the ACS.*