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Yusuf Hamied Department of Chemistry

 

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

Exploiting Locality in Full Configuration Interaction Quantum Monte Carlo for Fast Excitation Generation.
O Weser, A Alavi, GL Manni
– Journal of Chemical Theory and Computation
(2023)
19,
9118
xTC: An efficient treatment of three-body interactions in transcorrelated methods.
EM Christlmaier, T Schraivogel, P López Ríos, A Alavi, D Kats
– J Chem Phys
(2023)
159,
014113
Orders of magnitude increased accuracy for quantum many-body problems on quantum computers via an exact transcorrelated method
IO Sokolov, W Dobrautz, H Luo, A Alavi, I Tavernelli
– Physical Review Research
(2023)
5,
023174
Optimizing Jastrow factors for the transcorrelated method.
JP Haupt, SM Hosseini, P López Ríos, W Dobrautz, A Cohen, A Alavi
– The Journal of Chemical Physics
(2023)
158,
224105
Transcorrelated coupled cluster methods. II. Molecular systems.
T Schraivogel, EM Christlmaier, P López Ríos, A Alavi, D Kats
– The Journal of chemical physics
(2023)
158,
214106
TREXIO: A file format and library for quantum chemistry.
E Posenitskiy, VG Chilkuri, A Ammar, M Hapka, K Pernal, R Shinde, EJ Landinez Borda, C Filippi, K Nakano, O Kohulák, S Sorella, P de Oliveira Castro, W Jalby, PL Ríos, A Alavi, A Scemama
– Journal of Chemical Physics
(2023)
158,
174801
Importance-sampling FCIQMC: Solving weak sign-problem systems
N Liebermann, K Ghanem, A Alavi
– Journal of Chemical Physics
(2022)
157,
124111
Perturbation calculation of the uniform electron gas with a transcorrelated Hamiltonian.
H Luo, A Alavi
– The Journal of chemical physics
(2022)
157,
074105
Performance of a one-parameter correlation factor for transcorrelation: Study on a series of second row atomic and molecular systems.
W Dobrautz, AJ Cohen, A Alavi, E Giner
– J Chem Phys
(2022)
156,
234108
Combined unitary and symmetric group approach applied to low-dimensional Heisenberg spin systems
W Dobrautz, VM Katukuri, NA Bogdanov, D Kats, G Li Manni, A Alavi
– Physical Review B
(2022)
105,
195123
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Research Group

Research Interest Group

Telephone number

01223 762877

Email address

asa10@cam.ac.uk