Universal tight binding model for chemical reactions in solution and at surfaces. I. Organic molecules

Abstract

Articles you may be interested inAs is now well established, a first order expansion of the Hohenberg-Kohn total energy density functional about a trial input density, namely, the Harris-Foulkes functional, can be used to rationalize a non self consistent tight binding model. If the expansion is taken to second order then the energy and electron density matrix need to be calculated self consistently and from this functional one can derive a charge self consistent tight binding theory. In this paper we have used this to describe a polarizable ion tight binding model which has the benefit of treating charge transfer in point multipoles. This admits a ready description of ionic polarizability and crystal field splitting. It is necessary in constructing such a model to find a number of parameters that mimic their more exact counterparts in the density functional theory. We describe in detail how this is done using a combination of intuition, exact analytical fitting, and a genetic optimization algorithm. Having obtained model parameters we show that this constitutes a transferable scheme that can be applied rather universally to small and medium sized organic molecules. We have shown that the model gives a good account of static structural and dynamic vibrational properties of a library of molecules, and finally we demonstrate the model's capability by showing a real time simulation of an enolization reaction in aqueous solution.In two subsequent papers, we show that the model is a great deal more general in that it will describe solvents and solid substrates and that therefore we have created a self consistent quantum mechanical scheme that may be applied to simulations in heterogeneous catalysis. © 2014 AIP Publishing LLC.

Universal tight binding model for chemical reactions in solution and at surfaces. II. Water

“…Francisco, 1980). 18 The cutoff functions used in the present study are fifth order polynomials P 5 (x) that produce a smooth step between 1 and 0 with continuous second derivatives: It is straightforward to demonstrate that functionf (r) and its first two derivatives coincide with those of f (r) at r < r (1) cut , are equal to 0 at r > r…”

“…In Paper I 1 we gave a comprehensive account of the self consistent polarizable ion tight binding (PITB) theory. Further details can be found in Refs.…”

“…In the first, 1 referred to as Paper I in what follows, we presented a scheme for molecular dynamics simulations of organic molecules and here we show how the method is extended for systems in polar solvents.…”

Universal tight binding model for chemical reactions in solution and at surfaces. III. Stoichiometric and reduced surfaces of titania and the adsorption of water

“…As in Papers I and II, 1,2 we use the self consistent PITB theory described in Refs. [8][9][10][11].…”

“…Parameters of the polarizable ion tight binding (PITB) model, extended from the previous work 1,2 are listed in Sec. II and details of additional fitting procedures are given in Sec.…”