Theoretical Quantum Chemistry   Professor Peter Gill

 

We predict the behaviour of electrons and nuclei in atoms and molecules. In principle, people have known how to do this since 1926, when Erwin Schrodinger wrote down his celebrated equation. In practice, however, the equation is usually impossibly difficult and it is therefore necessary to devise methods that yield useful approximate solutions. The 1998 Nobel Prize for Chemistry was shared by Profs Walter Kohn and John Pople for their pioneering achievements in this area, which is called Quantum Chemistry.

We are inventing new quantum chemical methods and implementing these within a software package (Q-Chem) that is being developed as part of an international collaboration. The package is now used by hundreds of scientists around the world and is also an integral part of the popular Spartan package.

 

Current research activities

Intracules

An intracule is a function that gives the probability of observing two electrons in a given molecule with a specified separation. The separation can be in position space (which gives a position intracule) or momentum space (which gives a momentum intracule) but we have recently introduced a new function, the Wigner intracule W(u,v), that gives the probability of observing two electrons at a distance u and moving with relative momentum v. The Wigner intracule is a simple but powerful tool for understanding the motion of electrons in molecules.

Density functionals

At the moment,the most popular form of quantum chemistry is Density Functional Theory (DFT) but the accuracy of the results depends on the quality of the underlying density functionals. Many functionals have been developed during the last decade and we are particularly interested in construction of functionals that yield accurate predictions of molecular vibrational frequencies. We are also developing a new class of functionals that can be integrated analytically, without the need to resort to numerical quadrature.

Combinatorial problems

Some of the most challenging numerical problems (e.g. the travelling salesman, Full CI calculations, exact permutation significance tests) require a computational effort that increases exponentially (or faster) with the size of the problem. We are exploring new methods of computing these using algorithms whose computational costs increase only quadratically (or even linearly) with the problem size.

Annual Research Report   (PDF format)

 

Group members

Academic Staff:
Professor Peter Gill (Leader)   |   Dr Deborah Crittenden   |   Dr Andrew Gilbert   |   Dr Sergey Varganov

PhD students:
  Siu Hung Chien

 

Key publications

1. Y. Jung, A. Sodt, P.M.W. Gill and M. Head-Gordon, Auxiliary basis expansions for large-scale electronic structure calculations, Proceedings of the National Academy of Science (USA) 102 (2005) 6692-6697
2. S. Ghosh and P.M.W. Gill, Finite jellium models. I. Restricted Hartree-Fock calculations, Journal of Chemical Physics, 122 (2005) 154108/1-5
3. D.P. O'Neill and P.M.W. Gill, Benchmark correlation energies for small molecules, Molecular Physics, 103 (2005) 763-766
4. A.T.B. Gilbert, P.M.W. Gill and S.W. Taylor. Extracting atoms from molecular electron densities using integral equations. Journal of Chemical Physics, 120, (2004) 7887-7893.
5. C.Y. Lin, M.W. George and P.M.W. Gill. EDF2: A density functional for predicting molecular vibrational frequencies. Australian Journal of Chemistry, 57, (2004) 365-370.

>>more publications

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private web page: Peter Gill group photos

Professor P M W Gill Research School of Chemistry, Building 35 Australian National University Canberra ACT 0200 AUSTRALIA Ph: +61 2 6125 4258 Fx: +61 2 6125 0750 E-mail: pgill@rsc.anu.edu.au