Professor Ali Alavi FRS | Page 11 | Yusuf Hamied Department of Chemistry

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Professor of Theoretical Chemistry

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 of our research group website 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.

Publications

Efficient calculation of the exact exchange energy in periodic systems using a truncated Coulomb potential

J Spencer, A Alavi

– Physical Review B Condensed Matter and Materials Physics

(2008)

77,

193110

(doi: 10.1103/physrevb.77.193110)

Dipole Amplification: A Principle for the Self‐Assembly of Asymmetric Monomers on Metal Surfaces

OPH Vaughan, A Alavi, FJ Williams, RM Lambert

– Angewandte Chemie International Edition

(2008)

47,

2422

(doi: 10.1002/anie.200704172)

Electron correlation from path resummations: The double-excitation star

AJW Thom, GH Booth, A Alavi

– Phys. Chem. Chem. Phys.

(2008)

10,

652

(doi: 10.1039/b715773h)

Hydrogen absorption in bulk BC3:: A first-principles study

C Zhang, A Alavi

– J Chem Phys

(2007)

127,

214704

(doi: 10.1063/1.2802338)

Stochastic perturbation theory: A low-scaling approach to correlated electronic energies

AJW Thom, A Alavi

– Physical review letters

(2007)

99,

143001

(doi: 10.1103/PhysRevLett.99.143001)

Vibrational frequencies of CO on Pt(1 1 1) in electric field: A periodic DFT study

AY Lozovoi, A Alavi

– Journal of Electroanalytical Chemistry

(2007)

607,

140

(doi: 10.1016/j.jelechem.2007.02.030)

COLL 215-Switching on the dipole: A new principle for the self-assembly of asymmetric monomers on metal surfaces

OPH Vaughan, A Alavi, FJ Williams, RM Lambert

– ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY

(2007)

234,

(link to publication)

Structural surface investigations of cerium-zirconium mixed oxide nanocrystals with enhanced reducibility

JC Hernandez, AB Hungria, JA Perez-Omil, S Trasobares, S Bernal, PA Midgley, A Alavi, JJ Calvino

– Journal of Physical Chemistry C

(2007)

111,

9001

(doi: 10.1021/jp072466a)

Hot electrons and the approach to metallic behaviour in Kx(KCl)1 − x

PL Silvestrelli, A Alavi, M Parrinello, D Frenkel

– EPL (Europhysics Letters)

(2007)

33,

551

(doi: 10.1209/epl/i1996-00377-0)

Path resummations and the Fermion sign problem

A Alavi, AJW Thom

– Lecture Notes in Physics

(2006)

703,

685

(doi: 10.1007/3-540-35273-2_19)