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# Incrementally Corrected Periodic Local MP2 Calculations: I. The Cohesive Energy of Molecular Crystals

journal contribution

posted on 2013-12-10, 00:00 authored by Carsten Müller, Denis UsvyatA method for accurate
calculations of the cohesive energy of molecular
crystals is presented. The cohesive energy is evaluated as a sum of
several components. The major contribution is captured by periodic
Hartree–Fock (HF) coupled with the local Møller–Plesset
perturbation theory of second order (LMP2) with a triple-ζ basis
set. Post-MP2 corrections and corrections for the basis set incompleteness
are calculated from inexpensive incremental calculations with finite
clusters. This is an essential improvement with respect to the periodic
LMP2 method and allows for results of benchmark quality for crystalline
systems. The proposed technique is superior to the standard incremental
scheme as concerns the cluster size and basis set convergence of the
results. In contrast to the total energy or electron correlation energy,
which are evaluated in standard incremental calculations, post-MP2
and basis set corrections are rather insensitive to approximations
and converge quickly both in terms of the order of the increments
and the number of terms at a given order. Evaluation of the incremental
corrections within the sub-kJ/mol precision requires computing very
few of the most compact two-center and three-center non-embedded clusters,
making the whole correction scheme computationally inexpensive. This
method as well as alternative routes to compute the cohesive energy
via the incremental scheme are tested on two molecular crystals: carbon
dioxide (CO

_{2}) and hydrogen cyanide (HCN).