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Professor Ali Alavi FRS

Portrait of asa10

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.

 

Teaching

 

Please click on: http://www-alavi.ch.cam.ac.uk/teaching

 

Publications

 

Please click on: http://www-alavi.ch.cam.ac.uk/publications

Publications

Density matrices in full configuration interaction quantum Monte Carlo: Excited states, transition dipole moments, and parallel distribution
NS Blunt, GH Booth, A Alavi
– The Journal of Chemical Physics
(2017)
146,
244105
Stochastic multi-reference perturbation theory with application to the linearized coupled cluster method (vol 146, 044107, 2017)
G Jeanmairet, S Sharma, A Alavi
– J Chem Phys
(2017)
146,
239901
Projector Quantum Monte Carlo Method for Nonlinear Wave Functions
LR Schwarz, A Alavi, GH Booth
– Physical Review Letters
(2017)
118,
176403
Semistochastic Heat-Bath Configuration Interaction Method: Selected Configuration Interaction with Semistochastic Perturbation Theory
S Sharma, AA Holmes, G Jeanmairet, A Alavi, CJ Umrigar
– J Chem Theory Comput
(2017)
13,
1595
Combining Internally Contracted States and Matrix Product States To Perform Multireference Perturbation Theory
S Sharma, G Knizia, S Guo, A Alavi
– J Chem Theory Comput
(2017)
13,
488
Stochastic multi-reference perturbation theory with application to the linearized coupled cluster method
G Jeanmairet, S Sharma, A Alavi
– The Journal of Chemical Physics
(2017)
146,
044107
Assessment of multireference approaches to explicitly correlated full configuration interaction quantum Monte Carlo.
JAF Kersten, GH Booth, A Alavi
– The Journal of Chemical Physics
(2016)
145,
054117
Quasi-degenerate perturbation theory using matrix product states.
S Sharma, G Jeanmairet, A Alavi
– The Journal of chemical physics
(2016)
144,
034103
Stochastic Multiconfigurational Self-Consistent Field Theory.
RE Thomas, Q Sun, A Alavi, GH Booth
– Journal of Chemical Theory and Computation
(2015)
11,
5316
An excited-state approach within full configuration interaction quantum Monte Carlo
NS Blunt, SD Smart, GH Booth, A Alavi
– The Journal of chemical physics
(2015)
143,
134117
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Research Group

Research Interest Group

Telephone number

01223 762877

Email address

asa10@cam.ac.uk