Speaker
Description
The Hartree-Fock (HF) method is one of the most important methods of electronic structure theory. So there is interest in this algorithm, for example, within the framework of a future software ecosystem for high-precision multi-scale ab initio relativistic quantum modeling of atoms, molecules, and materials (part of the BUFO program [1]). But the conventional sequential program implementation of the HF algorithm is too slow and memory-intensive since the evaluation and storage of four-center molecular integrals are needed in HF to obtain the matrix elements of the Coulomb and exchange operators. Therefore, it is considered to be a key bottleneck of the algorithm. Several methods have been designed to speed up this part of the algorithm, one of which is known as resolution of identity approximation (RI) [2]. This method allows to skip evaluation and storage of four-center molecular integrals to vector-matrix operations with two- and three-center integrals and storage of them. The latter can be significantly or sometimes completely organized in RAM of several CPUs or GPUs, unlike four-center integrals. This organization gives a large performance gain because vector-matrix operations to obtain the matrix elements of the Coulomb and exchange operators can be efficiently done in parallel. Thus, if we want to obtain a highly efficient version of the HF algorithm, the most promising option is to develop the RI-HF version. It is done using the libcint library for calculating integrals [3] and using vector-matrix multiplications [4]. The results were compared with those in the ORCA program package [5].
[1] Oleynichenko, A. V., Rumyantsev A. S., Skripnikov, L. V., Seregin, M. M., Zaitsevskii, A. V., Eliav, E., Galigerov, V. S. , Kashpurovich, Yu. V., Stegailov, V. V., & Titov, A. V. Towards a software ecosystem for high-precision multi-scale ab initio relativistic quantum modeling of atoms, molecules and materials. The 28th International Scientific Conference of Young Scientists and Specialists (AYSS-2024).
[2] Vahtras, O., Almlöf, J., & Feyereisen, M. Integral approximations for LCAO-SCF calculations. Chemical Physics Letters, 213(5–6), 514–518 (1993).
[3] Sun, Q. Libcint: An efficient general integral library for Gaussian basis functions. Journal of Computational Chemistry, 36(22), 1664–1671 (2015).
[4] Glebov, I. O., & Poddubnyi, V. V. An Effective Algorithm of the Hartree–Fock Approach with the Storing of Two-Electron Integrals in the Resolution of Identity Approximation. Russian Journal of Physical Chemistry, 98, 617–625 (2024).
[5] Neese, F. (2011). The ORCA program system. Wiley Interdisciplinary Reviews Computational Molecular Science, 2(1), 73–78 (2011).
