N₂O in small para‐hydrogen clusters: Structures and energetics

Abstract

We present the minimum-energy structures and energetics of clusters of the linear N(2)O molecule with small numbers of para-hydrogen molecules with pairwise additive potentials. Interaction energies of (p-H(2))-N(2)O and (p-H(2))-(p-H(2)) complexes were calculated by averaging the corresponding full-dimensional potentials over the H(2) angular coordinates. The averaged (p-H(2))-N(2)O potential has three minima corresponding to the T-shaped and the linear (p-H(2))-ONN and (p-H(2))-NNO structures. Optimization of the minimum-energy structures was performed using a Genetic Algorithm. It was found that p-H(2) molecules fill three solvation rings around the N(2)O axis, each of them containing up to five p-H(2) molecules, followed by accumulation of two p-H(2) molecules at the oxygen and nitrogen ends. The first solvation shell is completed at N = 17. The calculated chemical potential oscillates with cluster size up to the completed first solvation shell. These results are consistent with the available experimental measurements.

Rotationally adiabatic pair interactions of para- and ortho-hydrogen with the halogen molecules F2, Cl2, and Br2

“…This yields two-dimensional potentials, depending on the orientation of the halogen molecule and the distance R, which is equivalent to an effective point-like H 2 molecule representing a certain rotational state. In most of the previous work found in the literature, [70][71][72][73][74] effects of H 2 rotation are eliminated by considering the free rotor ground state only, i.e., by isotropic averaging with respect to the rotational degrees of freedom. In this approximation, perturbations of the free rotor states due to the presence of an intermolecular potential are neglected.…”

“Adiabatic-hindered-rotor” treatment of the parahydrogen-water complex

“…Figure 4 shows that for a given orientation (θ , χ ), the equilibrium intermolecular distance of the AHR complex is about 0.1 a 0 shorter than the SPH, a result consistent with the stronger interaction. Overall, the substantial difference between the AHR and SPH potential energies excludes the possibility of treating pH 2 as a diabatic sphere 26,[28][29][30][31] in its interaction with H 2 O.…”

“…This fairly large energy gap suggests that it may be satisfactory to treat the pH 2 molecule in van der Waals complexes diabatically as a sphere. 26,[28][29][30][31] Under this approximation, performing a simple spherical average over the two degrees of freedom (spherical angles) describing the rotation of H 2 about its centre of mass effectively removes these coordinates, and large-scale simulations become much less expensive. However, such an approximation may be too crude when the interaction between pH 2 and its partner(s) is strong enough to substantially hinder its rotation by mixing the ground rotational state with excited states.…”

A new six-dimensional potential energy surface for H2–N2O and its adiabatic-hindered-rotor treatment

“…In addition, hydrogen clusters doped by small chromophore molecules have been studied extensively in order to obtain insight into the structure and dynamics of the micro-solvation environment of the dopant molecule. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Among reported spectroscopic studies of vdW complexes containing H 2 , Tang and McKellar found that the vibrational band origin of H 2 -N 2 O dimers is blueshifted, 4 while for the two similar complexes H 2 -CO 2 and H 2 -OCS, the vibrational band origins are slightly redshifted. 5,7 To obtain insight regarding the reason for these differences, an elaborate fivedimensional PES of the H 2 -N 2 O dimer that explicitly incorporated the asymmetric stretch coordinate (Q 3 ) of N 2 O while the other internal modes were fixed at their equilibrium vala) Authors to whom correspondence should be addressed.…”