Many-body effects on the structures and stability of Ba2+Xen(n= 1–39, 54) clusters

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.

Non-Relativistic Electronic-Structure Computation of Neutral and Cationic Systems [Fr2, Fr-AEM+ (AEM= Ca, Sr, Ba)]

The experimental field of ultracold ion-atom mixtures including an alkali-metal atom and an alkaline-earth-metal ion as well as of homonuclear alkali dimers has paved the way for creating and manipulating the ultracold molecules. The present paper is focused on a study of molecules such us francium dimer and a comparative spectroscopic investigation of the cationic systems Fr-(Ca⁺, Sr⁺, Ba⁺). We adopt a computational scheme without spin-orbit coupling reposed on the full configuration interaction and semi-empirical pseudo-potential theory of the atomic cores Fr⁺, Ca²⁺, Sr²⁺, and Ba²⁺ with extended and optimized basis sets. We have determined the adiabatic potentials with their relative spectroscopic constants, the electric dipole moments and the vibrational levels spacings for the ^1,3Σ_u,g⁺ and ^1,3Σ⁺ electronic states for Fr₂ and Fr-AEM⁺, respectively, correlated toward {Fr(7s) + Fr(7s, 7p, 6d, 8s, 8p)}, {Ca(4s², 4s4p, 4s3d), Sr(5s², 5s5p, 5s4d), Ba(6s², 6s6p, 6s5d) + Fr⁺}, and {Ca⁺(4s, 3d), Sr⁺(5s, 4d), Ba⁺(6s, 5d) + Fr(7s, 7p)}. The accuracy and reliability of the current results are discussed by comparing with theoretical data available in the literature. The occurrence of some avoided crossings between the neighboring electronic states is leading to a charge or excitation transfer for atom-ion collisions in the diverse charge or excited states. The Σ⁺-Σ⁺ transitions are determined in order to evaluate the future radiative lifetimes of vibrational states serving the direct laser cooling.

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.