The work of our group is primarily focused on the electron correlation problem - namely how to compute the correlation energy for an atom, molecule, or even solid, starting from a mean-field (say Hartree-Fock) description of the system. Our approach is to combine quantum chemical ideas with stochastic (Monte Carlo) techniques, which enable us to tackle problems which are very difficult to solve use standard quantum chemical techniques alone.
We are developing Quantum Monte Carlo algorithms adapted for electronic (and more generally Fermionic) problems by working in Slater determinant spaces. The central problem which is encountered is the infamous "Fermion sign problem", which results from electronic wavefunctions having both positive and negative amplitudes. Currently we are working on a novel population dynamics algorithm which propagates walkers in Slater determinant space according to a type of "stochastic cellular automaton" obeying simple rules. The movie on the home page shows an evolving population of walkers of positive and negative sign settling on the FCI wavefunction of a nitrogen dimer in a minimal basis - an archetypal multireference system. The remarkable aspect of this dynamics is the spontaneous symmetry breaking caused by annhilation processes, allowing the exact nodal surface of the nitrogen molecule, as expressed by the CI coefficients, molecule to appear. No fixed-node approximation is applied.
Further animations of this method in action can be viewed here.
Funding for our work comes from: EPSRC, University of Cambridge, Trinity College, Woolf Fisher Trust.
Computational resources are provided via the UK supercomputing facility in Edinburgh (HECToR), the European Distributed Extreme Initiative for Supercomputing Applications (DEISA), and Swiss supercomputing centre in Lugano (CSCS).
The following positions are currently available in our group:
(1) A post-doctoral research position is available in the group of Professor Ali Alavi, for the development and application of full CI quantum Monte Carlo to correlated electronic systems. Candidates should have (or be about to obtain) a PhD in theoretical chemistry or physics, with a strong grounding in many-electron quantum mechanics, including quantum chemistry or condensed matter physics. Experience with large-scale computations and parallel programming would be an advantage.
The post is available from January 2012. Applications should include a CV, publications list, contact details for three professional referees, and a completed form CHRIS/6 Parts I and III (downloadable from http://www.admin.cam.ac.uk/offices/hr/forms/chris6/), and should be sent to Professor Ali Alavi, Department of Chemistry, Lensfield Road, Cambridge CB2 1EW (email: email@example.com). Informal enquiries can be addressed to Professor Alavi.
Further particulars can be found on:
A PHD STUDENTSHIP
(2) An EPSRC-funded PhD studentship is available in the group of Professor Ali Alavi, for the development and application of full CI quantum Monte Carlo to correlated electronic systems. Candidates should have (or expect to obtain) at least the equivalent of a UK II.1 honours degree (and preferably a Masters) in chemistry or physics, with an interest in theoretical subjects. Candidates with a computer science or mathematics background with an interest in theoretical chemistry may also be suitable for this project, and are encouraged to make informal enquiries.
The studentship will provide a maintenance grant and tuition fees at the Home/EU rate. Non-EU nationals can be considered only if they already have the means to cover the fees differential for overseas students. The studentship is available from October 2012. Applications should include a CV, contact details for two academic referees, and should be sent to Professor Ali Alavi, Department of Chemistry, Lensfield Road, Cambridge CB2 1EW (email: firstname.lastname@example.org).
* Limit of tenure: 3.5 years
Quote Reference: MA09083,Closing Date: 31 December 2011