Title of the Thesis:

Towards High-Accuracy Auxiliary-Field Quantum Monte
Carlo: Methodological Advancements and Applications

Defense committee:

Michele Casula, Sorbonne Université, FR (reviewer)
Daniel A. Böse, Karl-Franzens-Universität Graz, AT (reviewer)
Georg Kresse (supervisor)
Markus Arndt (chair)

Abstract

In this work, we developed and applied the auxiliary-field quantum Monte Carlo (AFQMC) method for accurate electronic structure calculations.
AFQMC is a modern many-body approach that can outperform traditional high-accuracy quantum chemistry methods such as CCSD(T), while remaining computationally efficient.
We implemented a scalable Fortran-based AFQMC code and achieved excellent
performance across a range of molecules, including the HEAT dataset and water clusters.
We also addressed key methodological challenges such as time-step errors, size-
consistency issues, and the construction of accurate multideterminantal
trial wave functions using non-orthogonal configuration interaction (NOCI).
The resulting method combines accuracy, efficiency, and scalability, making AFQMC
a promising tool for high-precision large-scale electronic structure calculations.