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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.


X marks the spot: Accurate energies from intersecting extrapolations of continuum quantum Monte Carlo data.
SM Hosseini, A Alavi, P López Ríos
– The Journal of chemical physics
Toward Real Chemical Accuracy on Current Quantum Hardware Through the Transcorrelated Method
W Dobrautz, IO Sokolov, K Liao, PL Ríos, M Rahm, A Alavi, I Tavernelli
– Journal of Chemical Theory and Computation
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
xTC: An efficient treatment of three-body interactions in transcorrelated methods
EM Christlmaier, T Schraivogel, P López Ríos, A Alavi, D Kats
– The Journal of Chemical Physics
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
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
Transcorrelated coupled cluster methods. II. Molecular systems
T Schraivogel, EM Christlmaier, P López Ríos, A Alavi, D Kats
– J Chem Phys
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
– The Journal of chemical physics
Importance-sampling FCIQMC: Solving weak sign-problem systems.
N Liebermann, K Ghanem, A Alavi
– J Chem Phys
Perturbation calculation of the uniform electron gas with a transcorrelated Hamiltonian.
H Luo, A Alavi
– J Chem Phys
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Research Group

Research Interest Group

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01223 762877

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