Molecular grand-canonical ensemble density functional theory

The fundamental challenge of compound design, \textit{i.e.}~the reverse engineering of stable chemical compounds with predefined specific properties, originates in the high-dimensional and combinatorial nature of the \textit{chemical} space [1] which is spanned by the grand-canonical variables (superimposed particle densities of electrons and nuclei). A rigorous description of chemical space, using a grand-canonical multi-component density functional theory framework, will be presented [2]. Specifically, a total energy density functional for molecular systems in contact with an electron and a proton bath is introduced using Lagrange multipliers which correspond to the energetic response to changes of the elementary particle densities. Results will be shown for a molecular Fukui function, for finite temperature estimates of the redox potential of ammonia, and for alchemical variation of the intermolecular energy of formic acid interacting non-covalently with 10 proton systems [2,3]. Implications for rational compound design [4] and multi-scale modeling shall be discussed.\newline [1] P Kirkpatrick, C Ellis \textit{Nature} {\bf 432} 823 (2004) \newline [2] OAvL, M E Tuckerman \textit{J Chem Phys} {\bf 125} 154104 (2006) \newline [3] OAvL, M E Tuckerman \textit{submitted} \newline [4] OAvL, R Lins, U Rothlisberger \textit{Phys Rev Lett} {\bf 95} 153002 (2005)