“Divide-and-conquer” semiclassical molecular dynamics: An application to water clusters

Abstract

We present an investigation of vibrational features in water clusters performed by means of our recently established divide-and-conquer semiclassical approach [M. Ceotto, G. Di Liberto, and R. Conte, Phys. Rev. Lett. 119, 010401 (2017)]. This technique allows us to simulate quantum vibrational spectra of high-dimensional systems starting from full-dimensional classical trajectories and projection of the semiclassical propagator onto a set of lower dimensional subspaces. The potential energy surface employed is a many-body representation up to three-body terms, in which monomers and two-body interactions are described by the high level Wang-Huang-Braams-Bowman (WHBB) water potential, while, for three-body interactions, calculations adopt a fast permutationally invariant ab initio surface at the same level of theory of the WHBB 3-body potential. Applications range from the water dimer up to the water decamer, a system made of 84 vibrational degrees of freedom. Results are generally in agreement with previous variational estimates in the literature. This is particularly true for the bending and the high-frequency stretching motions, while estimates of modes strongly influenced by hydrogen bonding are red shifted, in a few instances even substantially, as a consequence of the dynamical and global picture provided by the semiclassical approach.

Vibrational investigation of nucleobases by means of divide and conquer semiclassical dynamics

“…For this reason, the initial kinetic energy of the first seven lowest frequency vibrational modes is set to zero, since rotational contributions would jeopardize the numerical convergence of the spectra. This strategy is similar to what has been done in previous semiclassical calculations, 70,71 and it does not represent a bias since the initial kinetic energy of the trajectory is reduced by only 5% below the harmonic ZPE value, which is obviously in excess with respect to the actual ZPE. The columns of Tables II and III, labeled "Harmonic", report the harmonic frequencies of both isomers.…”

Protonated glycine supramolecular systems: the need for quantum dynamics

“… 48 The method can deal with very high dimensional molecular and supra-molecular systems, and it is very accurate when compared to available exact vibrational quantum mechanical calculations. 49 , 50 Specifically, our DC-SCIVR method has been tested successfully against systems with up to hundreds of degrees of freedom, 48 and in particular it has been employed to study the vibrational features of the protonated water dimer, the Zundel cation. The results are very accurate (within a few wavenumbers) even for the vibrational bands of the proton doublet in the region of the O–H–O stretching frequency and associated with the proton transfer (∼1000 cm –1 ), when compared to exact grid-based quantum dynamics results on the same PES.…”

The formation mechanism of uranium and thorium hydride phosphorus: a systematically theoretical study

“…The vibrational zero-point energy (VZPE) is considered in all relative energies, and correction factors were used in vibration frequencies to take into account the inuence of anharmonic effects. [36][37][38] Electron localization function (ELF), quantum theory of atoms in molecules (QTAIM) and Mayer bond order are carried out. These analyses are completed using Multiwfn package, 39 the bond character, the charge distribution and metal valence population are completed using NBO in Gaussian 16 package.…”