QMCF MD Simulations of Composite Solutes

In the past decade, ab initio QM/MM molecular dynamics simulations, where the chemically most relevant subregion of the system is treated at Hartree-Fock or even higher level, while the remaining system is described by ab initio generated 2- and 3-body potential functions, have proven a most successful tool to reveal the structural details and the ultrafast dynamics of pure liquids and ions solvated in these liquids. Numerous properties of solvated species hardly accessible by contemporary experimental methods have been evaluated with the help of such simulations. The application of this method has its intrinsic limits, however, when more composite solutes, e.g. complexes with various ligands, become the focus of interest, as the construction of the necessary 2- and 3- body interaction potential energy surfaces and their subsequent fitting to analytical functions turns into a most tedious and sometimes even ambiguous procedure. A new simulation method recently developed by the applicant, the `QMCF MD` approach, overcomes this difficulty and allows ab initio simulations of solvated systems without the need of any such potential functions except those for solvent-solvent interactions. The basis of this method is a sufficiently large quantum mechanical (QM) region including the solute plus a full solvation layer, a large outer solvent box described classically (MM), but also incorporated as a perturbation (charge field, CF) into the QM Hamiltonian, and the explicit consideration of the fluctuating charges in the QM region in the evaluation of interactions between QM region and MM region. In the present project, this method should be further developed and applied to numerous composite solutes difficult to access by conventional QM/MM simulations. These solutes will rank from composite ions such as TiO2+ (resp. Ti(OH)2 2+ ), ClO4 - and Hg2 2+ to metal ion - ligand complexes of the MLn type, L being ligands such as Cl - , CN - , CO, NO or simple chelate formers, or a mixture of such ligands. These applications are expected to open the way to accurate simulations of more complex model systems of biologically relevant molecules such as the active centres of metalloenzymes, and thus to the evaluation of structure and, in particular, the fast dynamics of such systems in the aqueous environment of organisms

A large number of publications have appeared in international scientific journals of high impact, and 3 invited book contributions bring the total number of publications achieved in this project to 78 (without posters, Ph.D. And M.Sc. Theses). Further publications are submitted or in preparation. Numerous international visitors have shown much interest in the ongoing projects, and their visits have served to continue existing or start new co-operations. In this context a very valuable extension of the project work is seen in the co-operation with one of the most renowned experimental groups studying ions in solution, the group of Prof. Ingmar Persson in Uppsala/Sweden,and a cooperation with Prof. Enriques Sanchez-Marcos` group at the University of Sevilla/Spain. The work in the project has covered a wide range of hydrated metal ions from all parts of the periodic system of elements. It could also be shown that the new methodology developed in this project is capable of treating electronic excitation of the ions in solution, opening an access to realistic UV/VIS spectra of these ions. Further, the applicability of the method to treat solvation of neutral molecules and anions with weak solvent binding through H bonds has been demonstrated, and ultrafast dynamics of hydrolysing systems were also shown to be treatable. A large number of project coworkers have obtained their M.Sc. and/or Ph.D. Degree as a result of their thesis work within this project. The results of this project could be presented in several international conferences in the form of invited plenary and session lectures and posters.