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Yusuf Hamied Department of Chemistry

 
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 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

Spin-Pure Stochastic-CASSCF via GUGA-FCIQMC Applied to Iron–Sulfur Clusters
W Dobrautz, O Weser, NA Bogdanov, A Alavi, G Li Manni
– J Chem Theory Comput
(2021)
acs.jctc.1c00589
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
– The Journal of Chemical Physics
(2021)
155,
011102
Resolution of Low-Energy States in Spin-Exchange Transition-Metal Clusters: Case Study of Singlet States in [Fe(III)4S4] Cubanes
G Li Manni, W Dobrautz, NA Bogdanov, K Guther, A Alavi
– Journal of Physical Chemistry A
(2021)
125,
4727
Signatures of the BCS-BEC crossover in the yrast spectra of Fermi quantum rings
U Ebling, A Alavi, J Brand
– Physical Review Research
(2021)
3,
023142
A full configuration interaction quantum Monte Carlo study of ScO, TiO, and VO molecules
T Jiang, Y Chen, NA Bogdanov, E Wang, A Alavi, J Chen
– Journal of Chemical Physics
(2021)
154,
164302
Population control bias and importance sampling in full configuration interaction quantum Monte Carlo
K Ghanem, N Liebermann, A Alavi
– Physical Review B
(2021)
103,
155135
Structural and electronic properties of solid molecular hydrogen from many-electron theories
K Liao, T Shen, XZ Li, A Alavi, A Grüneis
– Physical Review B
(2021)
103,
054111
Electronic correlations and magnetic interactions in infinite-layer NdNiO2
VM Katukuri, NA Bogdanov, O Weser, J Van Den Brink, A Alavi
– Physical Review B
(2020)
102,
241112
The adaptive shift method in full configuration interaction quantum Monte Carlo: Development and applications.
K Ghanem, K Guther, A Alavi
– J Chem Phys
(2020)
153,
224115
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Research Group

Research Interest Group

Telephone number

01223 762877

Email address

asa10@cam.ac.uk