Bound-state energies in argon trimers via a variational expansion: The effects from many-body corrections

Computational Modeling: Up-to-Date Approaches and Cutting-Edge Applications from Clusters, Nanostructures to Bulk Systems

The contributions in this special theme collection, in honor to Prof. P. Villarreal, cover a broad variety of computational methodologies and experimental techniques, containing studies on gas phase, clusters and condensed phase systems.

Statistical properties of the rovibrational bound levels for Ar2Kr

We calculate the rovibrational bound levels with total angular momentum J = 0, 1 of ⁴⁰Ar₂⁸⁴Kr trimer using the slow variable discretization method combined with the finite-element method-discrete variable representation basis. The statistical distributions of the rovibrational levels for J^Π=0^e, 1^e, and 1^o symmetries are presented and the effects of the Axilrod-Teller potential term are considered. For the 0^e and 1^e symmetries, the Axilrod-Teller term makes the spectra become fully chaotic. However, for the 1^o symmetry, statistical properties depend mainly on the coupling between K = 0 and K = 1 and the Axilrod-Teller term has a small effect.

Eigen energies and the statistical distributions of the rovibrational levels of the bosonic van der Waals argon trimer

The eigen energies and the statistical distributions of the rovibrational levels (J = 0-2) of the bosonic van der Waals argon trimer were calculated using a full angular momentum three-dimensional finite element method. The influence of interatomic potentials on the vibrational levels and statistical properties of the trimer was discussed.

Bosonic helium droplets with cationic impurities: onset of electrostriction and snowball effects from quantum calculations

Variational Monte Carlo and diffusion Monte Carlo calculations have been carried out for cations such as Li(+), Na(+), and K(+) as dopants of small helium clusters over a range of cluster sizes up to about 12 solvent atoms. The interaction has been modeled through a sum-of-potential picture that disregards higher order effects beyond atom-atom and atom-ion contributions. The latter were obtained from highly correlated ab initio calculations over a broad range of interatomic distances. This study focuses on two of the most striking features of the microsolvation in a quantum solvent of a cationic dopant: electrostriction and snowball effects. They are discussed here in detail and in relation with the nanoscopic properties of the interaction forces at play within a fully quantum picture of the cluster features.

Microsolvation of Cationic Dimers in 4He Droplets: Geometries of (He)N (A = Li, Na, K) from Optimized Energies

Ab initio computed interaction forces are employed to describe the microsolvation of the A+2(2Sigma) (A=Li, Na, K) molecular ion in 4He clusters of small variable size. The minimum energy structures are obtained by performing energy minimization based on a genetic algorithm approach. The symmetry features of the collocation of solvent adatoms around the dimeric cation are analyzed in detail, showing that the selective growth of small clusters around the two sides of the ion during the solvation process is a feature common to all three dopants.

New method for calculating bound states: the A(1) states of Li(3) on the spin-aligned Li(3)(1 (4)A(')) potential energy surface

In this paper, we present a calculation for the bound states of A(1) symmetry on the spin-aligned Li(3)(1 (4)A(')) potential energy surface. We apply a mixture of discrete variable representation and distributed approximating functional methods to discretize the Hamiltonian. We also introduce a new method that significantly reduces the computational effort needed to determine the lowest eigenvalues and eigenvectors (bound state energies and wave functions of the full Hamiltonian). In our study, we have found the lowest 150 energy bound states converged to less than 0.005% error, and most of the excited energy bound states converged to less than 2.0% error. Furthermore, we have estimated the total number of the A(1) bound states of Li(3) on the spin-aligned Li(3)(1 (4)A(')) potential surface to be 601.

Calculation of argon trimer rovibrational spectrum

Rovibrational spectra of Ar3 are computed for total angular momenta up to J=6 using row-orthonormal hyperspherical coordinates and an expansion of the wave function on hyperspherical harmonics. The sensitivity of the spectra to the two-body potential and to the three-body corrections is analyzed. First, the best available semiempirical pair potential (HFDID1) is compared with our recent ab initio two-body potential. The ab initio vibrational energies are typically 1-2 cm-1 higher than the semiempirical ones, which is related to the slightly larger dissociation energy of the semiempirical potential. Then, the Axilrod-Teller asymptotic expansion of the three-body correction is compared with our newly developed ab initio three-body potential. The difference is found smaller than 0.3 cm-1. In addition, we define approximate quantum numbers to describe the vibration and rotation of the system. The vibration is represented by a hyper-radial mode and a two-degree-of-freedom hyperangular mode, including a vibrational angular momentum defined in an Eckart frame. The rotation is described by the total angular momentum quantum number, its projection on the axis perpendicular to the molecular plane, and a hyperangular internal momentum quantum number, related to the vibrational angular momentum by a transformation between Eckart and principal-axes-of-inertia frames. These quantum numbers provide a qualitative understanding of the spectra and, in particular, of the impact of the nuclear permutational symmetry of the system (bosonic with zero nuclear spin). Rotational constants are extracted from the spectra and are shown to be accurate only for the ground hyperangular mode.

Competitive bond breaking in floppy molecular trimers: HeNeH and HeNeH- calculations

Calculations for the J=0 bound states associated with the two title molecular systems are carried out using distributed Gaussian function approach and using the sum of two-body potential approximation to describe the overall interactions. The results yield one bound state for the neutral trimer and three bound states for the anionic triatom. The relative values of dissociation energies place the first dissociation threshold at the H emission for the neutral complex and at the He emission for the corresponding anion. The general spatial properties of the various bound states are analyzed on both systems.

Rovibrational Structures in Floppy Triatomics: Distributed Gaussian Functions Treatment for the Ne2H- System

The full sequence of the bound states for a very floppy triatomic complex, Ne2H- in its ground electronic state, are initially computed for the rotationless situation and employing a variational approach that expands the total nuclear wave function over a large set of symmetry-adapted, distributed Gaussian functions and employs accurate atom-atom potential energy data. The results are tested for numerical convergence, compared with the behavior of both its diatomic fragments, Ne2 and NeH-, and further compared with the results for the Ne3 case. The computational analysis is extended to the production of the rotational constants for the very nonclassical ground state vibrational configuration by making use of the previous findings. The method is shown to provide us with several illuminating details on the nanoscopic internal dynamics of this very weakly bound quantum aggregate.