Professor Ali Alavi FRS | Page 2 | Yusuf Hamied Department of Chemistry

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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

Full configuration interaction quantum Monte Carlo treatment of fragments embedded in a periodic mean field

EM Christlmaier, D Kats, A Alavi, D Usvyat

– J Chem Phys

(2022)

156,

154107

(doi: 10.1063/5.0084040)

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

– J Chem Phys

(2022)

156,

124704

(doi: 10.1063/5.0087031)

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

(doi: 10.1038/s41567-021-01439-1)

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

(doi: 10.1103/physrevb.104.235102)

Transcorrelated coupled cluster methods.

T Schraivogel, AJ Cohen, A Alavi, D Kats

– The Journal of chemical physics

(2021)

155,

191101

(doi: 10.1063/5.0072495)

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

(doi: 10.1021/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

(doi: 10.1103/physrevresearch.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

– Journal of Chemical Physics

(2021)

155,

011102

(doi: 10.1063/5.0055575)

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

– J Phys Chem A

(2021)

125,

4727

(doi: 10.1021/acs.jpca.1c00397)

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

(doi: 10.1103/PhysRevResearch.3.023142)