Abstract
In this paper, we report reimplementation of the core algorithms of relativistic coupled cluster theory aimed at modern heterogeneous high-performance computational infrastructures. The code is designed for parallel execution on many compute nodes with optional GPU coprocessing, accomplished via the new ExaTENSOR back end. The resulting ExaCorr module is primarily intended for calculations of molecules with one or more heavy elements, as relativistic effects on the electronic structure are included from the outset. In the current work, we thereby focus on exact two-component methods and demonstrate the accuracy and performance of the software. The module can be used as a stand-alone program requiring a set of molecular orbital coefficients as the starting point, but it is also interfaced to the DIRAC program that can be used to generate these. We therefore also briefly discuss an improvement of the parallel computing aspects of the relativistic self-consistent field algorithm of the DIRAC program.
Highlights
Computational chemistry is a standard tool in the analysis, design, and synthesis of molecular systems.[1]
The ExaCorr implementation that we describe here is based on the ExaTENSOR library,[24] a distributed numerical tensor algebra library for GPU-accelerated HPC platforms developed at the Oak Ridge Leadership Computing Facility (OLCF)
To check the property implementation, we compared the dipole moment, electric field gradient (EFG), and the nuclear quadrupole coupling constant (NQCC) of CHFClBr and UF6 for different implementations, which can be found in the Supporting Information; the output files are provided in a separate repository.[46]
Summary
Computational chemistry is a standard tool in the analysis, design, and synthesis of molecular systems.[1]. DFT does not allow for molecule-specific validations of the accuracy of its predictions This is possible for the wave-function-based methods, such as coupled cluster (CC) theory, for which extensions of the single-particle basis combined with an increase of the excitation level in the CC ansatz lead to a systematic improvement of the accuracy. The standard approaches to compute ground-state energies, molecular properties, and electronically excited states have all been generalized to relativistic theory as well, yielding methods that can provide very high accuracy in the electronic structure part of a calculation This is demonstrated in numerous small-molecule applications[6−10] for which steep scaling with the system size of the coupled cluster algorithm is not an issue. We want to enable the treatment of larger molecular systems with an all-electron correlated relativistic method that can be used to estimate the accuracy of different approximations for systems with significant correlation and relativistic effects
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