Towards structural optimization of gold nanoclusters with quantum Monte Carlo

We study the prospects of using quantum Monte Carlo techniques (QMC) to optimize the electronic wavefunctions and atomic geometries of gold compounds. Complex gold nanoclusters are widely studied for diverse biochemical applications, but the dynamic correlation and relativistic effects in gold set the bar high for reliable, predictive simulation methods. Here we study selected ground state properties of few-atom gold clusters by using density functional theory (DFT) and various implementations of the variational Monte Carlo (VMC) and diffusion Monte Carlo. We show that the QMC methods mitigate the exchange-correlation (XC) approximation made in the DFT approach: the average QMC results are more accurate and significantly more consistent than corresponding DFT results based on different XC functionals. Furthermore, we use demonstrate structural optimization of selected thiolated gold clusters with between 1 and 3 gold atoms using VMC forces. The optimization workflow is demonstrably consistent, robust, and its computational cost scales with n(b), where b < 3 and n is the system size. We discuss the implications of these results while laying out steps for further developments.

Automated summary

We study the potential use of quantum Monte Carlo techniques to optimize the electronic wavefunctions and atomic geometries of gold compounds. We show that these methods can mitigate the limitations of density functional theory and achieve more accurate and consistent results for gold nanoclusters. In addition, we demonstrate a robust and scalable optimization workflow for thiolated gold clusters with 1-3 gold atoms.