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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.

Publications

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
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
(2022)
156,
154107
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
(2022)
156,
124704
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
(2021)
18,
190
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
(2021)
104,
235102
Transcorrelated coupled cluster methods
T Schraivogel, AJ Cohen, A Alavi, D Kats
– J Chem Phys
(2021)
155,
191101
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
(2021)
17,
5684
Towards efficient and accurate ab initio solutions to periodic systems via transcorrelation and coupled cluster theory
K Liao, T Schraivogel, H Luo, D Kats, A Alavi
– Physical Review Research
(2021)
3,
033072
Binding curve of the beryllium dimer using similarity-transformed FCIQMC: Spectroscopic accuracy with triple-zeta basis sets
K Guther, AJ Cohen, H Luo, A Alavi
– J Chem Phys
(2021)
155,
011102
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Research Group

Research Interest Group

Telephone number

01223 762877

Email address

asa10@cam.ac.uk