Search

Reports on the viscosity and self-diffusion coefficients of carbon in the gas phase based on a first-principles interaction potential. Indications that transport coefficients increase monotonically with increasing temperature; Phenomenon ascribed to the interaction potentials between carbon molecules.

Abstract  The structures and stabilities of B n O and B n O2 clusters with n ≤ 6 are studied systematically by using density-functional theory. The lowest-energy structures of B n O clusters favor two-dimensional, and can be obtained from B n or B n−1O. For B n O2, unexpectedly, all of the most stable B n O2 clusters but B6O2 are linear. Furthermore, in B n O2 clusters, the longer the distance between two O atoms, the more stable the structure. To investigate the relative stability of considered clusters, binding energies per atom, reaction energies, and fragmentation energies are also calculated and discussed. [ABSTRACT FROM AUTHOR]

The geometries, stabilities, and electronic properties of Bnand AlBnclusters, up to n12, have been systematically investigated by using the density-functional approach. The results of Bnclusters are in good agreement with previous conclusions. When the Al atom is doped in Bnclusters, the lowest-energy structures of the AlBnclusters favor two-dimensional and can be obtained by adding one Al atom on the peripheral site of the stable Bnwhen n≤ 5. Starting from n6, the lowest-energy structures of AlBnclusters favor three-dimensional and can be described as an Al atom being capped on the Bnclusters. The average atomic binding energies, fragmentation energies, and second-order energy differences are calculated and discussed. Maximum peaks were observed for clusters of sizes n5, 8, 11, especially for the AlB8cluster, implying that these clusters possess relatively higher stability. The adiabatic IP and EA of AlBnand Bnclusters are discussed and compared with some available experimental results. A distinct phenomena for AlBnclusters is that all even n, but n10, have higher adiabatic ionization potentials than odd n. [ABSTRACT FROM AUTHOR]

The geometries, stabilities, and electronic and magnetic properties of YnAl (n=1–14) clusters have been systematically investigated by using density functional theory with generalized gradient approximation. The growth pattern for different sized YnAl (n=1–14) clusters is Al-substituted Yn+1 clusters and it keeps the similar frameworks of the most stable Yn+1 clusters except for Y9Al cluster. The Al atom substituted the surface atom of the Yn+1 clusters for n<9. Starting from n=9, the Al atom completely falls into the center of the Y-frame. The Al atom substituted the center atom of the Yn+1 clusters to form the Al-encapsulated Yn geometries for n>9. The calculated results manifest that doping of the Al atom contributes to strengthen the stabilities of the yttrium framework. In addition, the relative stability of Y12Al is the strongest among all different sized YnAl clusters, which might stem from its highly symmetric geometry. Mulliken population analysis shows that the charges always transfer from Y atoms to Al atom in all different sized clusters. Doping of the Al atom decreases the average magnetic moments of most Yn clusters. Especially, the magnetic moment is completely quenched after doping Al in the Y13, which is ascribed to the disappearance of the ininerant 4d electron spin exchange effect. Finally, the frontier orbitals properties of YnAl are also discussed. [ABSTRACT FROM AUTHOR]

The geometries, stabilities, and electronic properties of TiSin (n=2–15) clusters with different spin configurations have been systematically investigated by using density-functional theory approach at B3LYP/LanL2DZ level. According to the optimum TiSin clusters, the equilibrium site of Ti atom gradually moves from convex to surface, and to a concave site as the number of Si atom increases from 2 to 15. When n=12, the Ti atom in TiSi12 completely falls into the center of the Si outer frame, forming metal-encapsulated Si cages, which can be explained by using 16-electron rule. On the basis of the optimized geometries, various energetic properties are calculated for the most stable isomers of TiSin clusters, including the average binding energy, the highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) gap, fragmentation energy, and the second-order difference of energy. It is found that at size n=6,8,12 the clusters are more stable than neighboring ones. According to the Mulliken charge population analysis, charges always transfer from Si atoms to Ti atom. Furthermore, the HOMO-LUMO gaps of the most stable TiSin clusters are usually smaller than those of Sin clusters. [ABSTRACT FROM AUTHOR]

The geometries, stabilities, and electronic properties of AuLa ( n = 2-8) clusters have been systematically investigated by using density-functional theory. The results show that the doped La atom prefers to locate at the center site with the number of Au atom increasing from 2 to 8. Furthermore, the AuLa clusters are more stable than the Au clusters. The charges transfer from La atom to Au atoms at n = 2-4, but charge-transferring is reversed at n = 5. [ABSTRACT FROM AUTHOR]