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Self‐consistent field for fragmented quantum mechanical model of large molecular systems
Author(s) -
Jin Yingdi,
Su Neil Qiang,
Xu Xin,
Hu Hao
Publication year - 2016
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.24252
Subject(s) - fragment (logic) , electronic structure , quantum , computer science , krylov subspace , field (mathematics) , subspace topology , algorithm , statistical physics , computational science , chemistry , iterative method , computational chemistry , physics , quantum mechanics , mathematics , artificial intelligence , pure mathematics
Fragment‐based linear scaling quantum chemistry methods are a promising tool for the accurate simulation of chemical and biomolecular systems. Because of the coupled inter‐fragment electrostatic interactions, a dual‐layer iterative scheme is often employed to compute the fragment electronic structure and the total energy. In the dual‐layer scheme, the self‐consistent field (SCF) of the electronic structure of a fragment must be solved first, then followed by the updating of the inter‐fragment electrostatic interactions. The two steps are sequentially carried out and repeated; as such a significant total number of fragment SCF iterations is required to converge the total energy and becomes the computational bottleneck in many fragment quantum chemistry methods. To reduce the number of fragment SCF iterations and speed up the convergence of the total energy, we develop here a new SCF scheme in which the inter‐fragment interactions can be updated concurrently without converging the fragment electronic structure. By constructing the global, block‐wise Fock matrix and density matrix, we prove that the commutation between the two global matrices guarantees the commutation of the corresponding matrices in each fragment. Therefore, many highly efficient numerical techniques such as the direct inversion of the iterative subspace method can be employed to converge simultaneously the electronic structure of all fragments, reducing significantly the computational cost. Numerical examples for water clusters of different sizes suggest that the method shall be very useful in improving the scalability of fragment quantum chemistry methods. © 2015 Wiley Periodicals, Inc.