Molecular Potential Energy Surfaces by Interpolation

Significant Achievements, Anticipated Outcomes and Future Work

Prof. Michael A. Collins and Dr Gloria Moyano have continued development of the program package, Grow, which automatically constructs molecular potential energy surfaces (PES) to calculate chemical reaction dynamics in the gas phase. The package is freely available to researchers in Australia and overseas. Gloria Moyano has applied the Grow package to important interstellar reactions and reactions involved in ammonia chemistry. In collaboration with Prof. Leo Radom, Prof. Collins has investigated the dynamics of some ion-molecule reactions which are important examples of collision induced isomerisation. Prof. Collins has improved the PES for the reactions of atomic hydrogen and water at very high energies. This has lead to joint publications with groups in the UK, Spain and Singapore on this system, which is a benchmark problem in the development of theoretical reaction dynamics. Together with Mr Christopher Evenhuis, the methodology to deal with reactions which involve multiple electronic states has been partially developed. This is a difficult problem for a number of reasons, including the fact that quantum chemistry calculations do not directly supply all the information needed to calculate the forces on the atoms, and because the symmetry of the so-called diabatic potentials is not simple. When complete, this aspect of the program package will also be made freely available. A collaboration with Prof. Geert-Jan Kroes and Dr Cedric Crespos of the University of Leiden, resulted in the construction of potential energy surfaces for reactions of molecules on metal surfaces.

Computational Techniques Used

The project uses the ab initio quantum chemistry programs installed at the APAC National Facility. Almost the full range of ab initio and DFT methods have been employed over a range of chemical reactions. The PES construction is achieved using the Grow package which was developed with APAC National Facility support. This package consists of Unix scripts and Fortran programs. Many algorithms for linear algebra are employed. The package also simulates chemical reaction dynamics. The computational tasks are substantial and could only be achieved by virtue of the computational power of the APAC National Facility resources, including the ability to run programs in parallel.

Publications, Awards and External Funding

External Funding and Awards

None.

Publications

M. Brouard, I. Burak, D. Minayev, P. O'Keee, C. Vallance, F. J. Aoiz, L. Banares, J. F.Castillo, Dong H. Zhang, and M. A. Collins, The dynamics of the H + D2O Æ OD + HD reaction at 2.5 eV, J. Chem. Phys. 118 (2003) 1162-1174.
J.F. Castillo, M.A. Collins, F.J. Aoiz, and L. Banares Quasi-classical trajectory study of the dynamics of the H + N2O reaction on a new potential energy surface J. Chem. Phys., 118 (2003) 7303-7312.
M. A. Collins and L. Radom Proton-transport catalysis, proton abstraction and proton exchange in HF + HOC+ and H2O + HOC+ and analogous deuterated reactions J. Chem. Phys., 118 (2003) 6222.
M. Brouard, I. Burak, S. Marinakis, D. Minayev, P. O'Keefe, C. Vallance, F.J. Aoiz, L. Banares, J.F. Castillo, D.H. Zhang, D. Xie, M. Yang, S.-Y. Lee, M. A. Collins The cross-section for the H + H2O abstraction reaction: experiment and theory. Physical Review Letters, 90 (2003) 093201.
G. E. Moyano and M. A. Collins Interpolated potential energy surface and classical dynamics for HD + H3+ and D2 + H3+. J. Chem. Phys.119 (2003) 5510-5517.
Multi-dimensional potential energy surface determination by modified Shepard interpolation for a molecule-surface reaction: H2 + Pt(111) C. Crespos, M.A. Collins, E. Pijper, and G.J. Kroes Chemical Physics Letters, 376 (2003) 566-575.