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Acceleration of ab initio molecular dynamics (AIMD) simulations can be reliably achieved by extrapolation of electronic data from previous timesteps. Existing techniques utilize polynomial least-squares regression to fit previous steps’ Fock or density matrix elements. In this work, the recursive Burg ‘linear prediction’ technique is shown to be a viable alternative to polynomial regression, and the extrapolation-predicted Fock matrix elements were three orders of magnitude closer to converged elements. Accelerations of 1.8–3.4× were observed in test systems, and in all cases, linear prediction outperformed polynomial extrapolation. Importantly, these accelerations were achieved without reducing the MD integration timestep.

Polynomial extrapolation of response (‘z-vector’) elements is shown to reduce the cost of correlated-wavefunction, classical ab initio molecular dynamics. Demonstrations with resolution-of-the-identity Moller–Plesset perturbation theory (RI-MP2) show that the number of response equation iterations is reduced by a factor of 2–3, thereby enabling accelerated MP2 dynamics. Coupled with previously demonstrated Fock matrix extrapolation, the combined iterative SCF and z-vector calculations are reduced to a minority share of the total calculation. Though demonstrated for MP2, these methods can also be generalized to higher levels of electron correlation or excited state methods.

We report the geometries of two distorted T-shaped benzene dimer structures optimized at the RI-MP2/aug-cc-pVTZ level of theory. At the extrapolated RI-MP2/aug-cc-pV(TQ)Z level, the Cs over atom and Cs over bond configurations were found to be lower in energy than the conventionally accepted C2v T-shaped structure by 0.146 and 0.163 kcal/mol, respectively. When DCCSD(T)/6-311+G(2df,p) corrections were included, these structures remained lower in energy than the C2v reference by 0.127 and 0.132 kcal/mol, respectively, with Cs over bond as the minimum energy T-shaped structure. While not the focus of this Letter, we also report that the C2v T-shaped configuration is stabilized by 0.31 kcal/mol over the C2h parallel-displaced configuration at the DCCSD(T)/aug-cc-pVTZ approximation to the CCSD(T)/CBS limit. � 2007 Elsevier B.V. All rights reserved.