Development and parallel implementation of selected configuration interaction methods
Creators: name: Garniron, Yann
Publisher: name: Zenodo
Year: 2019
Subjects: subject: Computational Chemistry
subject: Perturbation theory
subject: Configuration Interaction
subject: Monte Carlo
subject: https://en.wikipedia.org/wiki/Computational_chemistry

description: This thesis, whose topic is quantum chemistry algorithms, is made in the context of the change in paradigm that has been going on for the last decade, in which the usual sequential algorithms are progressively replaced by parallel equivalents. Indeed, the increase in processors' frequency is challenged by physical barriers, so increase in computational power is achieved through increasing the number of cores.<br> However, where an increase of frequency mechanically leads to a faster execution of a code, an increase in number of cores may be challenged by algorithmic barriers, which may require adapting of even changing the algorithm. Among methods developed to circumvent this issue, we find in particular Monte-Carlo methods (stochastic methods), which are intrinsically "embarrassingly parallel", meaning they are by design composed of a large number of independent tasks, and thus, particularly well-adapted to massively parallel architectures. In addition, they often are able to yield an approximate result for just a fraction of the cost of the equivalent deterministic, exact computation.<br> During this thesis, massively parallel implementations of some deterministic quantum chemistry algorithms were realized. Those methods are: CIPSI, Davidson diagonalization, computation of second-order perturbation, shifted-Bk, Multi-Reference Coupled-Cluster. For some of these, a stochastic aspect was introduced in order to improve their efficiency. All of them were implemented on a distributed task model, with a central process distributing tasks and collecting results. In other words, slave nodes can be added during the computation from any location reachable through Internet. The efficiency for the implemented algorithms has been studied, and the code could give way to numerous applications, in particular to obtain reference energies for difficult molecular systems.<br>
description: {"references": ["Garniron, Yann, et al. \"Hybrid stochastic-deterministic calculation of the second-order perturbative contribution of multireference perturbation theory.\" The Journal of chemical physics 147.3 (2017): 034101. https://doi.org/10.1063/1.4992127", "Loos, Pierre-Fran\u00e7ois, et al. \"A Mountaineering Strategy to Excited States: Highly Accurate Reference Energies and Benchmarks.\" Journal of chemical theory and computation 14.8 (2018): 4360-4379. https://pubs.acs.org/doi/abs/10.1021/acs.jctc.8b00406", "Giner, Emmanuel, et al. \"A Jeziorski-Monkhorst fully uncontracted multi-reference perturbative treatment. I. Principles, second-order versions, and tests on ground state potential energy curves.\" The Journal of chemical physics 146.22 (2017): 224108. https://doi.org/10.1063/1.4984616", "Scemama, Anthony, et al. \"Deterministic construction of nodal surfaces within quantum Monte Carlo: the case of FeS.\" Journal of chemical theory and computation 14.3 (2018): 1395-1402. https://pubs.acs.org/doi/abs/10.1021/acs.jctc.7b01250", "Garniron, Yann, et al. \"Selected configuration interaction dressed by perturbation.\" The Journal of chemical physics 149.6 (2018): 064103. https://doi.org/10.1063/1.5044503", "Garniron, Yann, et al. \"Alternative definition of excitation amplitudes in multi-reference state-specific coupled cluster.\" The Journal of chemical physics 146.15 (2017): 154107. https://doi.org/10.1063/1.4980034"]}