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Department of Chemistry

 

My primary research focusses on using multiple solutions to the Self-Consistent Field equations as a basis for Configuration Interaction (CI) correlation methods. To achieve this, I am currently involved in researching and developing Holomorphic Hartree-Fock theory. In normal Hartree-Fock theory, the energy functional is not holomorphic in it's arguments (the MO coefficients), and so there is no well defined complex derivative. Futhermore, as geometry changes cause the coefficients within the Hartree-Fock equations to change, stationary points of the functional disappear.

We define a new 'holomorphic' Hartree-Fock energy functional by removing the complex conjugation of coefficients from the expectation value of the energy. We anticipate that this new functional should have a constant number of stationary points as the geometry changes and will be well-behaved in the complex plane. For H2, these states represent the continuation of standard UHF states beyond the Coulson-Fischer point and extend in the complex direction. Whilst these stationary points' holomorphic energies are not particularly relevant, their locations vary smoothly with geometric changes.

The set of all h-UHF states provides a powerful basis for performing a non-orthogonal CI (NOCI) expansion at a much lower cost than Full-CI. In comparison to truncated CI, the NOCI wavefunction maintains the size-extensivity of the underlying h-UHF states and recovers a significant amount of the correlation energy. We are currently developing reliable methods for finding these h-UHF states whilst exploring the topology of the holomorphic energy functional.

Publications

General Approach for Multireference Ground and Excited States Using Nonorthogonal Configuration Interaction
HGA Burton, AJW Thom
– Journal of chemical theory and computation
(2019)
15,
4851
PT-Symmetry in Hartree--Fock Theory
HGA Burton, AJW Thom, P-F Loos
– Journal of Chemical Theory and Computation
(2019)
15,
4374
Field-Programmable Gate Arrays and Quantum Monte Carlo: Power Efficient Co-processing for Scalable High-Performance Computing
S Cardamone, JRR Kimmitt, HGA Burton, TJ Todman, S Li, W Luk, AJW Thom
– International Journal of Quantum Chemistry
(2019)
119,
e25853
General Approach for Multireference Ground and Excited States using Non-Orthogonal Configuration Interaction
HGA Burton, AJW Thom
– J Chem Theory Comput
(2019)
15,
4851
Complex adiabatic connection: A hidden non-Hermitian path from ground to excited states
HGA Burton, AJW Thom, P-F Loos
– The Journal of Chemical Physics
(2019)
150,
041103
Holomorphic Hartree-Fock Theory: The Nature of Two-Electron Problems.
HGA Burton, M Gross, AJW Thom
– Journal of Chemical Theory and Computation
(2018)
14,
607
Microscopic Marangoni Flows Cannot Be Predicted on the Basis of Pressure Gradients.
Y Liu, R Ganti, HGA Burton, X Zhang, W Wang, D Frenkel
– Phys Rev Lett
(2017)
119,
224502
Holomorphic Hartree-Fock Theory: An Inherently Multireference Approach
HGA Burton, AJW Thom
– J Chem Theory Comput
(2016)
12,
167

Research Group

Telephone number

01223 336423 (shared)

Email address

hb407@cam.ac.uk