The quantum structure of anionic hydrogen clusters

Abstract

A flexible and polarizable interatomic potential has been developed to model hydrogen clusters interacting with one hydrogen anion, (H)H, in a broad range of sizes n = 1-54 and parametrized against coupled cluster quantum chemical calculations. Using path-integral molecular dynamics simulations at 1 K initiated from the putative classical global minima, the equilibrium structures are found to generally rely on icosahedral shells with the hydrogen molecules pointing toward the anion, producing geometric magic numbers at sizes n = 12, 32, and 44 that are in agreement with recent mass spectrometry measurements. The energetic stability of the clusters is also connected with the extent of vibrational delocalization, measured here by the fluctuations among inherent structures hidden in the vibrational wave function. As the clusters grow, the outer molecules become increasingly free to rotate, and strong finite size effects are also found between magic numbers, associated with more prominent vibrational delocalization. The effective icosahedral structure of the 44-molecule cluster is found to originate from quantum nuclear effects as well, the classical structure showing no particular symmetry.

Snowball formation for Cs+ solvation in molecular hydrogen and deuterium

“…Our goal is to investigate whether well-defined and compact shells are formed and what their structure is. In addition, since the H 2 -Cs + interaction is very anisotropic, we believe that it is worth studying the H 2 /D 2 orientational effects 10,31,32 by explicitly taking into account their rotational degrees of freedom and comparing with the more widely used pseudoatom model. The importance of three-body (3B) induction forces [33][34][35][36] is assessed as well.…”

Absorption Spectra of Electrified Hydrogen Molecules

“…We have not attempted to quantify the mutual couplings just described, but there is a growing literature on ab initio structural models of molecular hydrogen nanoclusters, and such models could be used to assess the electrical environments in which the H 2 moieties reside. For nanoclusters of the type H H n 2 -( ) , structures have been determined using a variety of quantum chemical methods (e.g., Huang et al 2011;Calvo & Yurtsever 2018;Mohammadi et al 2020). We note that Calvo & Yurtsever (2018) obtained results in accord with the mass spectroscopy of anion clusters undertaken by Renzler et al (2016), who demonstrated the existence of "magic numbers" n = 12, n = 32, and n = 44, consistent with icosahedral solvation shells.…”

“…For nanoclusters of the type H H n 2 -( ) , structures have been determined using a variety of quantum chemical methods (e.g., Huang et al 2011;Calvo & Yurtsever 2018;Mohammadi et al 2020). We note that Calvo & Yurtsever (2018) obtained results in accord with the mass spectroscopy of anion clusters undertaken by Renzler et al (2016), who demonstrated the existence of "magic numbers" n = 12, n = 32, and n = 44, consistent with icosahedral solvation shells.…”

Absorption spectra of electrified hydrogen molecules

“…For nanoclusters of the type H − (H 2 ) n structures have been determined using a variety of quantum chemical methods (e.g. Huang et al 2011;Calvo & Yurtsever 2018;Mohammadi et al 2020). We note that Calvo & Yurtsever (2018) obtained results in accord with the mass spectroscopy of anion clusters undertaken by Renzler et al (2016), who demonstrated the existence of "magic numbers" n = 12, n = 32 and n = 44, consistent with icosahedral solvation shells.…”