posted on 2021-11-29, 20:34authored byNuno Barbosa, Marco Pagliai, Sourab Sinha, Vincenzo Barone, Dario Alfè, Giuseppe Brancato
Grimme’s
dispersion-corrected density functional theory
(DFT-D) methods have emerged among the most practical approaches to
perform accurate quantum mechanical calculations on molecular systems
ranging from small clusters to microscopic and mesoscopic samples,
i.e., including hundreds or thousands of molecules. Moreover, DFT-D
functionals can be easily integrated into popular ab initio molecular dynamics (MD) software packages to carry out first-principles
condensed-phase simulations at an affordable computational cost. Here,
starting from the well-established D3 version of the dispersion-correction
term, we present a simple protocol to improve the accurate description
of the intermolecular interactions of molecular clusters of growing
size, considering acetonitrile as a test case. Optimization of the
interaction energy was performed with reference to diffusion quantum
Monte Carlo calculations, successfully reaching the same inherent
accuracy of the latter (statistical error of ∼0.1 kcal/mol
per molecule). The refined DFT-D3 model was then used to perform ab initio MD simulations of liquid acetonitrile, again showing
significant improvements toward available experimental data with respect
to the default correction.