Structural, energetic and response electric properties of cyclic selenium clusters: an ab initio and density functional theory study

Abstract

The geometries, relative stabilities, binding energies, second-order difference of total energy (D 2 E), vertical ionization energies (VIEs), vertical electron affinities (VEAs) and dipole polarizabilities of neutral Se 2 and cyclic Se n (n = 3-12) clusters have been systematically investigated using conventional ab initio [HF, MP2, MP3, MP4, CCSD, CCSD(T)] and density functional theory (B3LYP, CAM-B3LYP) levels with the Dunning's correlation-consistent (cc-pVDZ, aug-cc-pVDZ, d-aug-ccpVDZ and aug-cc-pVTZ) and Sadlej (POL and POL-DK) basis sets. For each cluster size, various structural isomers have been considered and optimized to search for the lowest-energy structure. The effects of the geometry, basis set and theoretical level on the calculated properties have been discussed. The relative stability of the clusters has been analyzed using binding energy per atom, D 2 E and VIE-VEA gap. The computed binding energies and VIEs have been compared with the available observed data. The calculated properties show a strong dependence upon the size and geometry of the cluster. The even-numbered Se n with n = 6 and 8 are predicted to be relatively stable clusters. The physico-chemical properties of selenium clusters have been compared to those of the sulphur homologues. On passing from sulphur to selenium clusters the binding energy per atom decreases, whereas the mean dipole polarizability per atom increases.

Uncharged Selenium Rings as Terminal and Bridging Ligands in Selenium‐Rich Iridium Clusters

“…The average Se–Se distance [238.9(1) pm] in Ir 2 Se 9 Cl 6 is about 5 pm longer than in the molecular form of the element [average Se–Se in α‐Se 8 : 233.6(6) pm],3 but close to the bond length in the helical chains of trigonal selenium [237.3(5) pm] 1. Quantum‐chemical calculations for an isolated Se 9 ring predicted a rather similar conformation with C 2 symmetry and bond lengths from 236.1 to 238.8 pm as well as bond angles from 102.5 to 109.1° 19. The corresponding bond angles in the coordinating nonaselenium ring in Ir 2 Se 9 Cl 6 are substantially smaller [93.3(1) to 97.3(1)°].…”

“…The Se 7 ring adopts a boat conformation, and thus differs from the chair‐like Se 7 in Re 2 (μ‐I) 2 (CO) 6 (Se 7 ) 18. Although the Se 7 isomers are almost isoenergetic – the chair less than 1 kcal · mol –1 more stable than the boat19 – the latter has not been found up to now.…”

“…Se–Se bond lengths in the Se 6 ring range from 218 to 250 pm and bond angles from 97 to 107°. For an isolated cyclo ‐Se 6 with D 3 d symmetry values of 238.2 pm and 101.7° were calculated 19. The chair‐Se 6 in the cluster compound PdBr 2 Se 6 is closer to the highly symmetric case, featuring bond lengths of 233.5(2) to 238.3(2) pm and angles of 96.2(1) to 101.8(1)° 6…”

“…The reported distances and angles for the chair‐Se 7 are 230.9(3)–255.8(3) pm and 99.3(1)–104.3(1)°. The calculated values of an isolated boat‐Se 7 molecule are 227.0 to 257.5 pm and 101.2 to 107.8° (density functional theory, B3LYP with correlation‐consistent cc‐pVDZ basis set) 19. In the two boat cases, the longest bonds are between Se14 and Se20.…”

Laser Ablation Synthesis of Gold Selenides by using a Mass Spectrometer as a Synthesizer: Laser Desorption Ionization Time‐of‐Flight Mass Spectrometry

“…[23][24][25][26][27][28][29][30][31] The structure of selenium clusters has been extensively studied. [30,[32][33][34] Progress in nanotechnology is required for development of new materials for publications including photovoltaics, optoelectronics, and imaging. To achieve this, new routes of synthesis are needed.…”