A new scheme for fixed node diffusion quantum Monte Carlo with pseudopotentials: improving reproducibility and reducing the trial-wave-function bias

Fixed node diffusion quantum Monte Carlo (FN-DMC) is an increasingly used computational approach for investigating the electronic structure of molecules, solids, and surfaces with controllable accuracy. It stands out among equally accurate electronic structure approaches for its favorable cubic scaling with system size, which often makes FN-DMC the only computationally affordable high-quality method in large condensed phase systems with more than 100 atoms. In such systems FN-DMC deploys pseudopotentials to substantially improve efficiency. In order to deal with non-local terms of pseudopotentials, the FN-DMC algorithm must use an additional approximation, leading to the so-called localization error. However, the two available approximations, the locality approximation (LA) and the T-move approximation (TM), have certain disadvantages and can make DMC calculations difficult to reproduce. Here we introduce a third approach, called the determinant localization approximation (DLA). DLA eliminates reproducibility issues and systematically provides good quality results and stable simulations that are slightly more efficient than LA and TM. When calculating energy differences — such as interaction and ionization energies — DLA is also more accurate than the LA and TM approaches. We believe that DLA paves the way to the automization of FN-DMC and its much easier application in large systems.

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Fabian wins Best Poster prize at the MMM Hub conference!

The second annual Materials & Molecular Modelling (MMM) Hub Conference and User Meeting took place on 3-4 September. Many excellent talks demonstrated how the computational resources provided by the MMM Hub are used to tackle challenges in many areas of biological, chemical, and physical research. This was also illustrated by more than 50 posters, spanning […]


Science and sports in York

Last weekend, the ICE group gathered in York for the International Materials Simulation Workshop. Current and former members as well as collaborators talked about their recent projects and discussed how to tackle society’s big challenges, utilize advancements in methodology and make the most of fruitful collaborations. The meeting highlighted the diverse range of problems that […]


Triple Triathlon at Castle Howard in support of WaterAid

The ICE group will be participating in the Castle Triathlon series for the third year in a row. This time, three relays teams are going to compete at Castle Howard, near York, on 21 July. They will be swimming, cycling and running a combined distance of roughly 280 km! As part of the tradition, the […]


Open postdoc position (University of Manchester & ICE group)

A 2-year postdoc position is available in the Condensed Matter Physics group at the University of Manchester. The project will be carried out in collaboration with the ICE group and involves developing and applying theoretical models to understand the anomalous dielectric behaviour of water under confinement (Fumagalli et al. Science 360, 1339-1342, 2018). You can […]


Angelos sets world record at the London Marathon!

Angelos set a new world record for the “fastest marathon dressed as a scientist (male)” at this year’s London Marathon, finishing in 3:22:51. Congratulations! He also managed to raise more than £3000 in support of WaterAid, an international charity working to provide clean water and decent toilets to people all over the world. Many thanks […]


Welcome Julia!

The ICE group has a new member: Julia will be working on C-H activation at single-atom alloy catalysts. The project involves collaboration with Michail Stamatakis from UCL’s Department of Chemical Engineering. We hope you will have a pleasant and productive time in the ICE group!


Nature Reviews Chemistry on surface premelting of water ice published!

In a recently published Nature Reviews Chemistry article, titled “Surface premelting of water ice”, Ben Slater and Angelos review the current understanding of the quasi-liquid layer (QLL) that forms on the surface of ice. The review describes how advances in experimental and computational techniques furthered our understanding in the years since Faraday first postulated the […]


Angelos is trying to set a new world record!

Angelos will be running this year’s London Marathon with the aim of setting a new world record for the “fastest marathon dressed as a scientist (male)”. He is running in support of WaterAid, an international charity working to provide clean water and decent toilets to people all over the world. To find out more and […]


Patrick wins Best Poster prize at the TYC Student Day!

For his contribution “A Machine Learning Potential for Carbon”, Patrick was awarded a Best Poster prize at this year’s TYC Student Day! He was one of the four winners chosen from more than 30 poster presentations, which highlighted the excellent research conducted within the Thomas Young Centre. Patrick had also won the Best Poster prize […]


INCITE grant awarded for quantum Monte Carlo project!

The proposal titled “New Frontiers for Material Modeling via Machine Learning Techniques with Quantum Monte Carlo” was awarded a 2019 Innovative and Novel Computational Impact on Theory and Experiment (INCITE) grant by the U.S. Department of Energy’s Office of Science. The project lead by Dario Alfè and in collaboration with Gábor Csányi in Cambridge involves […]


Group gatherings