An efficient fragment-based approach for predicting the ground-state energies and structures of large molecules.
An efficient fragment-based approach for predicting the ground-state energies and structures of large molecules at the Hartree-Fock (HF) and post-HF levels is described. The physical foundation of this approach is attributed to the "quantum locality" of the electron correlation energy and the HF total energy, which is revealed by a new energy decomposition analysis of the HF total energy proposed in this work. This approach is based on the molecular fractionation with conjugated caps (MFCC) scheme (Zhang, D. W.; Zhang, J. Z. H. J. Chem. Phys. 2003, 119, 3599), by which a macromolecule is partitioned into various capped fragments and conjugated caps formed by two adjacent caps. We find that the MFCC scheme, if corrected by the interaction between non-neighboring fragments, can be used to predict the total energy of large molecules only from energy calculations on a series of small subsystems. The approach, named as energy-corrected MFCC (EC-MFCC), computationally achieves linear scaling with the molecular size. Our test calculations on a broad range of medium- and large molecules demonstrate that this approach is able to reproduce the conventional HF and second-order Moller-Plesset perturbation theory (MP2) energies within a few millihartree in most cases. With the EC-MFCC optimization algorithm described in this work, we have obtained the optimized structures of long oligomers of trans-polyacetylene and BN nanotubes with up to about 400 atoms, which are beyond the reach of traditional computational methods. In addition, the EC-MFCC approach is also applied to estimate the heats of formation for a series of organic compounds. This approach provides an appealing approach alternative to the traditional additivity rules based on either bond or group contributions for the estimation of thermochemical properties.
Li
Shuhua
S
Department of Chemistry, Institute of Theoretical and Computational Chemistry, Lab of Mesoscopic Chemistry, Nanjing University, Nanjing 210093, People's Republic of China. shuhua@nju.edu.cn
Li
Wei
W
Fang
Tao
T
D006096:Gramicidin / Q000737:chemistry; D007473:Ion Channels / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry; D011487:Protein Conformation; D013816:Thermodynamics
D007473:Ion Channels; D010455:Peptides; D010940:Plant Proteins; D006096:Gramicidin; C011080:polyglycine; C024934:crambin protein, Crambe abyssinica