Quasi-freestanding silicene with massless Dirac fermion characteristics has been successfully obtained by oxygen intercalation.

Researchers predict a new ice clathrate structure as the most stable ice polymorph with the lowest density in a negative-pressure region.

Abstract

Using genetic algorithm combined with density functional theory calculations, we performed global search for the most stable structures of (WO₃)_n clusters for n = 2–12. Small (WO₃)_n clusters with n = 3 or 4 adopt ring-like configurations with W–O alternating arrangement. Starting from (WO₃)₈, the tungsten oxide clusters transform to symmetric spherical-like cages. The relative stability, HOMO–LUMO gap, electronic states of these (WO₃)_n clusters were discussed. Analysis of wavefunctions of frontier orbitals and electron density of states shows that the valence bands are dominated by the 2p electrons from oxygen and the conduction bands are mainly contributed by the 5d states from tungsten.

Abstract

Unbiased search by first-principles simulated annealing revealed irregular cage configurations for medium-sized B_n clusters (namely, boron fullerene) with n = 32–56, which are more stable than the previously proposed symmetric cages. The stability of these irregular cages can be understood by the three-center bonds as well as the polygonal holes on the cage surface. The delocalized distribution of molecular orbitals as well as the negative nucleus-independent chemical shifts (NICS) values for each boron cage indicates strong aromaticity.

Abstract

Lowest-energy structures of odd-sized cationic ${\text{P}}_{2m+1}^{+}$ (m = 1–12) clusters have been determined from first-principles simulated annealing followed by more accurate geometry optimization within the framework of density functional theory. For ${\text{P}}_n^{+}$ with n > 11, the current global minimum structures are more favorable than those previously reported ones. A structural motif based on P₇, P₈, P₉, and P₁₀ building blocks and P₂ bridge was revealed for the medium-sized ${\text{P}}_n^{+}$ clusters.

Abstract

The most stable structures of polyhydroxylated metallofullerene Gd@C₈₂(OH)_x (x = 1–24) were investigated using density functional theory calculations. After examining a number of structural isomers, some rules about the locations of hydroxyl groups on the endohedral fullerene cage of Gd@C₈₂ were proposed. The hydroxylated carbon atoms tend to enclose two opposite six-membered rings for the most stable Gd@C₈₂(OH)₁₂ and seven six-membered rings for the most stable Gd@C₈₂(OH)₂₄, respectively. The hydroxyl groups prefer to locate on para-position of the six-membered ring or meta-position of the five-membered ring.

Abstract

The lowest-energy structures were obtained for Ga_nN_n clusters (n = 4–12) using gradient-corrected density functional theory. For each cluster size, a number of structural isomers were constructed and optimized. Crossover from ring to cage-like structures were found at Ga₈N₈. The observed cage-like configurations consisting of six-membered rings with gallium–nitrogen alternative arrangement can be viewed as embryo of wurtzite structure of gallium nitride crystal. The size-dependence of cluster properties such as binding energy, HOMO–LUMO gaps, ionization potentials, electron affinities, and Mulliken charges have been computed and analyzed. The bonding characteristics of the Ga_nN_n clusters were discussed.