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