Ab initiostudy of Ba+Arn(n= 1–4) clusters: spectroscopic constants and vibrational energy levels

Structures and stability of K+ cation solvated in Arn clusters

The solvation of K+ cation plays an important role in various phenomena such as biological procedures, geological time, and archaeological properties. Monte Carlo (MC) simulation and DFT method are employed to study the structural and energetic characteristics of the K + Arn (n = 1-14) clusters. The potential model (PM) and the Basin-Hopping (BH) method are the foundation of the MC simulation. The pairwise PM (PW-PM) is improved by introducing the N-body interactions via the polarizable potential model (PPM). On the other side, the DFT functional M05-2X, combined with the 6-311++G(3d2f,2p) basis set, and the Grimme dispersion correction GD3 was used to deeply investigate the geometrical properties and the relative stability of the K + Arn clusters. Starting from n = 12, a structural transition from square antiprism (SA) to icosahedron (ICOS) form is detected. Additionally, the PPM allows us to examine the largest sizes (n = 15-54). Herein, the first ICOS layers are found for n = 12 and 54 cluster sizes, respectively. The binding energy and the second energy difference as a function of cluster size are used to evaluate the relative stability of K + Arn clusters. The obtained data are in concordance with the available results in the literature.

Microsolvation of lithium cation in xenon clusters: An octahedral growth pattern

The structural and energetic proprieties for the Li ⁺ Xe_n (n = 1-18) clusters are investigated using both Basin-Hopping combined with Potential Model description (BH-PM) and DFT methods. A structural transition from tetrahedral (4 coordination) form to octahedral (6 coordination) one is observed for n = 6. Above this size, all structures have an octahedral core. The cubic-face-centered arrangement for xenon atoms is detected for Li ⁺ Xe₁₄. To the best of our knowledge, the Li ⁺ Xe_n (n = 1-18) clusters are studied in the present work for the first time using the DFT theoretical approach. The M062X functional combined with aug-cc-pVDZ (for Li) and def2-TZVP (for Xe) basis sets reproduces accurately the CCSD(T) potential energy curve of Li + Xe system. Atom-Centered Density Matrix Propagation (ADMP) molecular dynamic calculations have been carried. Moreover, we investigate the larger sizes n = 31-35, 44, and 55 for the first time using the BH-PM theoretical approach. The closing of the first and second octahedron shells are proved for the n = 6 and 34 sizes, respectively. The relative stabilities of the Li ⁺ Xe_n molecules are also studied by computing the total energy, the binding energy per atoms for each size n. Then, the second energy difference between the size n and its two near neighbors allows identifying the magic number series. Our present data are analyzed, discussed and compared with the available theoretical and experimental data.

Solvation of lithium ion in helium clusters: Structural properties and relative stabilities

Structural study and relative stabilities of Li⁺-doped helium clusters Li⁺He_n (n = 1-18) has been reported in this work using two theoretical protocols. The first one is based on the basin-hopping optimization technique, where the total energy of each cluster is described by an additive model describing Li⁺-He and He-He interactions. The second one is the DFT calculations, in which the initial structures are generated by ABCluster algorithm and CALYPSO software. The CSA shape was found where the first solvation shell is completed at n = 10. The relative stabilities of Li⁺He_n (n = 1-18) clusters have been discussed based on the variation of the binding energy, second-order difference in energy, fragmentation energy and HOMO-LUMO energy gap as a function of the cluster size. The results showed that Li⁺He₁₀ is the most stable cluster. The dipole moment is calculated and showed the polar character of the Li⁺He_n clusters. Finally, the interatomic interactions have been examined topologically by the means of AIM and non-covalent reduced density gradient (NC-RDG) analyses.

Adiabatic and Diabatic Investigation of Numerous Electronic States for the Alkali Dimer FrNa

The current paper reports a global investigation of all excited states below the ionic limit Fr⁺Na^- of FrNa molecule following diabatic and adiabatic representations. The adiabatic and diabatic potential energy curves (PECs) for Σ⁺, Π, and Δ symmetries have been calculated for a dense grid of internuclear distances. The transition and permanent dipole moments (TDM and PDM) have been reported for both representations. Regarding the pseudopotential approach and full valence configuration interaction (FCI), the ab initio computation has been performed. Furthermore, the diabatization method was achieved by the use of the variational effective Hamiltonian theory (VEH). This latter served to assess the nonadiabatic coupling between the treated adiabatic states and to eliminate it employing a suitable unitary transformation matrix. The detailed computation of the PECs and PDM and TDM curves of the ground and excited states play a key role to coordinate experimental efforts in order to create cold and ultracold molecules in their ground stable rovibrational levels.

Interaction potentials and transport properties of Ba, Ba+, and Ba2+ in rare gases from He to Xe

A highly accurate, consistent set of ab initio interaction potentials is obtained for the title systems at the coupled cluster with singles, doubles, and non-iterative triples level of theory with extrapolation to the complete basis set limit. These potentials are shown to be more reliable than the previous potentials based on their long-range behavior, equilibrium properties, collision cross sections, and transport properties.