# Theoretical Chemistry

theochemOur main research topics are Quantum Monte Carlo methods and Chemical Bonding. Quantum Monte Carlo, QMC, is a stochastic technique for solving the Schrödinger Equation. We apply QMC methods mainly for the electronic Schrödinger equation and calculate energy differences such as reaction energies, activation barriers, and the gaps between different states of the same molecule.

The diffusion quantum Monte Carlo variant, DMC, is one of the most accurate methods for electron structure calculations with the additional advantage of allowing for highly parallel computer code. This is a most important feature as computer hardware has developed recently and will develop for at least another decade to computer systems with very many cores. QMC codes are highly efficient on massively parallel computers with many thousand cores.

Due to the stochastic nature QMC allows to employ highly accurate but compact many-electron wave functions. Through the analysis of our compact wave functions new ways of insight into chemical bonding becomes possible, in particular into the many-electron nature of wave function that is ignored in the typical orbital analysis because orbitals are one-electron functions.

theochem

Our group has been developing its own QMC programme called „amolqc“ over more than a decade. The code features strong multideterminant and optimisation capabilities.

A. Lüchow, Quantum Monte Carlo methods, Wiley Interdisciplinary Reviews, Comp. Mol. Sci., Vol. 1, 388-402, 2011, DOI: 10.1002/wcms.40

A. Lüchow, Maxima of |Ψ|2: A connection between quantum mechanics and Lewis structures, J. Comput. Chem., 35, 854 – 864, 2014, DOI: 10.1002/jcc.23561