Pairwise Model Potential and DFT Study of Li+Nen Clusters (n = 1-20): The Structural, Electronic, and Thermodynamic Properties.

The structural properties, relative stabilities, electronic, and thermodynamic properties, of Li+Nen (n = 1-20) clusters have been studied based on a pairwise model and density functional theory (DFT) methods. In the pairwise method, the potential energy surface considered interactions between Li+Ne, Ne - Ne, and many-body term. For the DFT calculations, the B3LYP functional combined with the 6-311 + + G (2d,2p) basis sets has been employed. In both methods, the Li+Ne6 cluster demonstrated high stability with an octahedral structure, where the Li+ cation was surrounded by Ne atoms. Thus, the octahedral Li+Ne6 structure was considered to be the core for larger cluster sizes. Relative stabilities were assessed based on binding energies, second-order differences of energies, transition dipole moment, and HOMO-LUMO energy gaps. Furthermore, thermodynamic properties were calculated, revealing that the formation process of Li+Nen clusters is endothermic and nonspontaneous.

Potential Energy Surface and Bound States of Ne-Li2+(X2Σg+) van der Waals Complex Based on Ab Initio Calculations.

Theoretical studies of the potential energy surface and vibrational bound states calculations were performed for the ground state of the Ne-Li2+(X2Σg+) van der Waals (vdW) complex. The intermolecular interactions were investigated by using an accurate monoconfigurational RCCSD(T) method and large basis sets (aug-cc-pVnZ, n = T, Q, 5), extrapolated to the complete basis set (CBS) limit. In turn, the obtained raw data from RCCSD(T)/CBS(Q5) calculations were numerically interpolated using the Morse + vdW model and the Reproducing Kernel Hilbert Space (RKHS) polynomial method to generate analytic expressions for the 2D-PES. The RKHS interpolated PES was then used to assess the bound states of the Ne-Li2+(X2Σg+) system through nuclear quantum calculations. By studying the aspect of the potential energy surface, the analysis sheds light on the behavior of the Ne-Li2+(X2Σg+) complex and its interactions between repulsive and attractive forces with other particles. By examining the vibrational states and wave functions of the system, the researchers were able to gain a better understanding of the behavior of the Ne-Li2+(X2Σg+) complex. The calculated radial and angular distributions for all even and odd symmetries are discussed in detail. We observe that the radial distributions exhibit a more complicated nodal structure, representing stretching vibrational behavior in the neon atom along its radial coordinate. For the highest bound states, the situation is very different, and the energies surpass the angular barrier.

Structural, Spectroscopic, and Dynamic Properties of Li2+(X2∑g+) in Interaction with Krypton Atom.

We report a computational study of the potential energy surface (PES) and vibrational bound states for the ground electronic state of Li2+Kr. The PES was calculated in Jacobi coordinates at the Restricted Coupled Cluster method RCCSD(T) level of calculation and using aug-cc-pVnZ (n = 4 and 5) basis sets. Afterward, this PES is extrapolated to the complete basis set (CBS) limit for correction. The obtained interaction energies were, then, interpolated numerically using the reproducing kernel Hilbert space polynomial (RKHS) approach to produce analytic expressions for the 2D-PES. The analytical PES is used to solve the nuclear Schrodinger equation to determine the bound states' eigenvalues of Li2+Kr for a J = 0 total angular momentum configuration and to understand the effects of orientational anisotropy of the forces and the interplay between the repulsive and attractive interaction within the potential surface. In addition, the radial and angular distributions of some selected bound state levels, which lie below, around, and above the T-shaped 90° barrier well, are calculated and discussed. We note that the radial distributions clearly acquire a more complicated nodal structure and correspond to bending and stretching vibrational motions "mode" of the Kr atom along the radial coordinate, and the situation becomes very different at the highest bound states levels with energies higher than the T-shaped 90° barrier well. The shape of the distributions becomes even more complicated, with extended angular distributions and prominent differences between even and odd states.

Spectroscopic Properties of the Alkali-Krypton Diatomic M-Kr (M = Rb, Cs, and Fr) van der Waals Systems Including the Spin-Orbit Coupling.

Using an ab initio approach based on pseudopotential technique, pair potential approach, core polarization potentials, and large Gaussian basis sets, we investigate interaction of heavy alkali-krypton diatomic M-Kr (M = Rb, Cs, and Fr) van der Waals dimers. In this context, the core-core interactions for M+-Kr (M = Rb, Cs, and Fr) are calculated at coupled-cluster single and double excitation (CCSD) level and included in the total potential energy. Therefore, the potential energy curves are performed for 14 electronic states: eight of 2Σ+ symmetry, four of 2Π symmetry, and two of 2Δ symmetry. Furthermore, for each M-Kr dimer, the spin-orbit coupling has been considered for the B2Σ+, A2Π, 32Σ+, 22Π, 52Σ+, 32Π, and 12Δ states. In addition, the transition dipole moment has been determined, including the spin-orbit effect using the rotational matrix issued from the spin-orbit potential energy calculations.