Computational Modelling Group

Seminar  23rd September 2011 2 p.m.  Building 27, Room 2003

New Developments in Semiempirical MO Theory for Drug and Materials Design. (MGMS Lecture Tour Seminar)

Professor Dr Tim Clark
Computer-Chemie-Centrum, Interdisciplinary Center for Molecular Materials, Excellence Cluster “Engineering of Advanced Materials”, Friedrich-Alexander-Universität, Erlangen, Germany and Centre for Molecular Design, University of Portsmouth

Web page
AMBER, Biomathematics, C, CASTEP, Complex Systems, Computer Science, Density functional Theory, Education, FFT, Fortran, Gaussian, HPC, Iridis, Linux, Materials, Molecular Dynamics, Molecular Mechanics, Monte Carlo, Multi-physics, Multi-scale, Multigrid solvers, Multipole methods, Nanoscale Assemblies, NWCHEM, Onetep, Optimisation, ProtoMS, Quantum Chemistry, Scientific Computing, Software Engineering, Structural biology, Systems biology
Chris-Kriton Skylaris

Semiempirical (NDDO-based, MNDO-like) molecular orbital (MO) theory has led a life in the shadows for several decades, probably because “more respectable” techniques, such as density-functional theory, have become applicable to quite large molecules, including transition-metal complexes. However, the great strengths of semiempirical MO theory (speed, scaling, one-electron properties, and excited states) remain.

Two independent parameterizations (PM6 and AM1*) for the first-row transition metals are now available, so that these elements can be treated successfully. Classical dispersion potentials have been added to standard parameterizations in the same spirit as DFT-D.

We have developed a massively parallel code that brings calculations on 100,000 atoms within reach on 1,000 processors with high efficiency, but also gives super-scalar performance on 8-32 processors, for instance on dual or quad-core nodes. Similarly, geometry optimizations on datasets of 100,000 drug-sized molecules and more are possible in a weekend on an eight-core node. These capabilities open new possibilities and applications of semiempirical MO theory.

Among these is the use of Pulay’s UNO-CAS technique to give reliable band gaps for semiconductors, which, combined with a newly developed direct optimization algorithm for the UHF density matrix, also allows calculations on conductors for the first time.

These developments provide a powerful tool for materials modeling, in particular for spectroscopic and electronic properties, but also for high-quality quantitative structure-property relationships without resorting to an atoms-and-bonds picture of molecules.


Dr Chris-Kriton Skylaris