Category Archives: Group news

Welcome! Welcome!

We are very excited to welcome the new additions to our group. From the left Dr. James Womack, who has returned after a postdoc with the Skylaris group in Southampton. Ollie who completed his MChem undergraduate degree with us earlier this year, Jillisa and Harry who are both part of the TMCS CDT.

Welcome, Kieron!

 

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We are very excited and honoured to welcome Prof Kieron Burke to Bristol for his sabbatical visit. Kieron is here as a Benjamin Meaker Visiting Professor, a scheme provided by the Institute for Advanced Studies. The plan is to work together on a range of areas at the interface between DFT and wavefunction methods. Kieron will be giving various talks and seminars during his visit (details to follow) and a short graduate-level course on exact properties of exchange and correlation functionals in DFT.

 

Congratulations!

Congratulations to Tim Wiles, who passed his PhD viva yesterday, and becomes the first TMCS student to graduate from my group! Tim worked on the Unsöld correlation functional, which we’re now finding allows the construction of accurate DFT approximations with extraordinarily low self-interaction errors. More on that in an up-coming publication…

Congratulations also to former group member Mainak Sadhukhan, who just started a faculty position at the Indian Institute of Technology, Kanpur. Mainak worked in the group as a Royal Society Newton International Fellow, before moving on to work with Alexandre Tkatchenko in Luxembourg.

Welcome to new group members

We’re delighted to welcome Susannah Bourne-Worster and Zack Williams to the group!

Susannah just completed her DPhil with Prof Peter Hore at the University of Oxford, and was awarded a prestigious three-year fellowship by the Royal Commission for the Exhibition of 1851. She will be working on our project on understanding efficiency of energy transport in photosynthesis.

Zack completed year-one of the TMCS programme and has joined the group for his doctoral research. He will be picking up Tim’s project on correlation functionals using the Unsöld approximation.

Unsöld functional – a new hybrid functional for correlation

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There are about four or five distinct ingredients used in modern density functionals:

  • integrals of functions of the density and its gradients (GGAs, etc)
  • inclusion of the kinetic energy density in such expressions (meta-GGAs)
  • a fraction of exact Hartree–Fock exchange (or a length-scale-screened variant)
  • a contribution from a wavefunction-based correlation method like MP2 or RPA

Now there is another:

Tim Wiles and F R Manby, ‘Wavefunction-like Correlation Model for Use in Hybrid Density Functionals’, J. Chem. Theory Comput., Article ASAP, DOI: 10.1021/acs.jctc.8b00337.

In this paper we introduce the UW12 correlation functional:

  • an explicit functional of occupied orbitals (i.e. a functional  of the 1-RDM)
  • an F12-like model of dynamic electron correlation
  • can be self-consistently optimized in a straightforward way
  • most of the complicated stuff handled through familiar DFT quadrature
  • no double-summation over virtual orbitals, so fast basis-set convergence

This functional can be used as a viable (and hybrid) alternative to use of MP2 in double-hybrid functionals, as we demonstrate in this paper. Our hybrid XCH-BLYP-UW12 functional has only one parameter, and is competitive with more highly parameterised  double hybrids for reaction barrier test sets.

If you don’t have access and want to read the paper, just email Fred.

Congratulations to Tim for publishing this work!