Symmetry can dramatically reduce the computational cost （running time and memory allocation） of Self-Consistent-Field ab initio calculations for crystalline systems. Crucial for running time is use of symmetry in th...Symmetry can dramatically reduce the computational cost （running time and memory allocation） of Self-Consistent-Field ab initio calculations for crystalline systems. Crucial for running time is use of symmetry in the evaluation of one- and two-electron integrals, diagonalization of the Fock matrix at selected points in reciprocal space, reconstruction of the density matrix. As regards memory allocation, full square matrices （overlap, Fock and density） in the Atomic Orbital （AO） basis are avoided and a direct transformation from the packed AO to the SACO （Symmetry Adapted Crystalline Orbital） basis is per- formed, so that the largest matrix to be handled has the size of the largest sub-block in the latter basis. We here illustrate the effectiveness of this scheme, following recent advancements in the CRYSTAL code, concerning memory allocation and direct basis set transformation. Quantitative examples are given for large unit cell systems, such as zeolites （all-silica faujasite and silicalite MF1） and garnets （pyrope）. It is shown that the full SCF of 3D systems containing up to 576 atoms and 11136 Atomic Orbitals in the cell can be run with a hybrid functional on a single core PC with 500 MB RAM in about 8 h.展开更多
基金Compagnia di San Paolo for financial support(Progetti di Ricerca di Ateneo-Compagnia di San Paolo-2011-Linea 1A,progetto ORTO11RRT5)Claudio Zicovich-Wilson acknowledges financial support from Mexican CONACyT through project CB-178853
文摘Symmetry can dramatically reduce the computational cost （running time and memory allocation） of Self-Consistent-Field ab initio calculations for crystalline systems. Crucial for running time is use of symmetry in the evaluation of one- and two-electron integrals, diagonalization of the Fock matrix at selected points in reciprocal space, reconstruction of the density matrix. As regards memory allocation, full square matrices （overlap, Fock and density） in the Atomic Orbital （AO） basis are avoided and a direct transformation from the packed AO to the SACO （Symmetry Adapted Crystalline Orbital） basis is per- formed, so that the largest matrix to be handled has the size of the largest sub-block in the latter basis. We here illustrate the effectiveness of this scheme, following recent advancements in the CRYSTAL code, concerning memory allocation and direct basis set transformation. Quantitative examples are given for large unit cell systems, such as zeolites （all-silica faujasite and silicalite MF1） and garnets （pyrope）. It is shown that the full SCF of 3D systems containing up to 576 atoms and 11136 Atomic Orbitals in the cell can be run with a hybrid functional on a single core PC with 500 MB RAM in about 8 h.
