Towards High Performance Relativistic Electronic Structure Modelling: The EXP-T Program Package
Modern challenges arising in the fields of theoretical and experimental physics require new powerful tools for high-precision electronic structure modelling; one of the most perspective tools is the relativistic Fock space coupled cluster method (FS-RCC).
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Petersburg Nuclear Physics Institute named by B.P. Konstantinov of NRC “Kurchatov Institute”, Gatchina, Russia [email protected], zaitsevskii [email protected] Department of Chemistry, Lomonosov Moscow State University, Moscow, Russia 3 School of Chemistry, Tel Aviv University, Tel Aviv, Israel [email protected]
Abstract. Modern challenges arising in the fields of theoretical and experimental physics require new powerful tools for high-precision electronic structure modelling; one of the most perspective tools is the relativistic Fock space coupled cluster method (FS-RCC). Here we present a new extensible implementation of the FS-RCC method designed for modern parallel computers. The underlying theoretical model, algorithms and data structures are discussed. The performance and scaling features of the implementation are analyzed. The software developed allows to achieve a completely new level of accuracy for prediction of properties of atoms and molecules containing heavy and superheavy nuclei. Keywords: Relativistic coupled cluster method · High performance computing · Excited electronic states · Heavy element compounds
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Introduction
Nowadays first-principle based electronic structure modelling is widely recognized as a powerful tool for solving both fundamental and applied problems in physics and chemistry [1]. A bulk of modern experiments in fundamental physics employing atomic and molecular systems seem to be hardly implementable or even senseless without theoretical predictions and assessments; some recent and the most striking examples are experiments for the electron electric dipole moment search [2], design of laser-coolable molecular systems [3] and spectroscopy of short-lived radioactive atoms and molecules [4,5]. Probably the most intriguing applications of quantum chemical modelling to fundamental problems are associated with molecules containing heavy and superheavy elements [6]; these applications require theoretical predictions to be accurate enough to be useful. For example, recent spectroscopic investigations of short-lived radioactive systems (No, Lr, RaF) required predicted excitation energies to be accurate c Springer Nature Switzerland AG 2020 V. Voevodin and S. Sobolev (Eds.): RuSCDays 2020, CCIS 1331, pp. 375–386, 2020. https://doi.org/10.1007/978-3-030-64616-5_33
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up to 200–500 cm−1 in order to plan spectroscopic experiment, reduce its cost crucially and decode experimentally observed spectrum. Such an outstanding accuracy is unreachable without careful treatment of the so-called relativistic effects, completely changing even the qualitative picture of electronic states and properties [7]. One of the most promising electronic structure models suitable for solution of such problems is the relativistic coupled cluster (RCC) theory [8] and its extensions to excited electronic states [9,10]. Despite such advantages of these methods as correct physical behaviour, conceptual simplicity and controllable accuracy, rather severe drawbacks are to b
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