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Yusuf Hamied Department of Chemistry

Portrait of asa10

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.


Importance-sampling FCIQMC: Solving weak sign-problem systems
N Liebermann, K Ghanem, A Alavi
– The Journal of chemical physics
Perturbation calculation of the uniform electron gas with a transcorrelated Hamiltonian.
H Luo, A Alavi
– J Chem Phys
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
– The Journal of chemical physics
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
General embedded cluster protocol for accurate modeling of oxygen vacancies in metal-oxides.
BX Shi, V Kapil, A Zen, J Chen, A Alavi, A Michaelides
– The Journal of Chemical Physics
Full configuration interaction quantum Monte Carlo treatment of fragments embedded in a periodic mean field.
EM Christlmaier, D Kats, A Alavi, D Usvyat
– The Journal of chemical physics
Enhancement of superexchange due to synergetic breathing and hopping in corner-sharing cuprates
NA Bogdanov, G Li Manni, S Sharma, O Gunnarsson, A Alavi
– Nature Physics
Benchmark study of Nagaoka ferromagnetism by spin-adapted full configuration interaction quantum Monte Carlo
S Yun, W Dobrautz, H Luo, A Alavi
– Physical Review B
Transcorrelated coupled cluster methods.
T Schraivogel, AJ Cohen, A Alavi, D Kats
– The Journal of Chemical Physics
Spin-Pure Stochastic-CASSCF via GUGA-FCIQMC Applied to Iron-Sulfur Clusters
W Dobrautz, O Weser, NA Bogdanov, A Alavi, G Li Manni
– Journal of Chemical Theory and Computation
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Research Group

Research Interest Group

Telephone number

01223 762877

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