Icosahedral and Ring‐Shaped Allotropes of Arsenic

Abstract

We predict the existence of two novel families of arsenic nanostructures: icosahedral cages and ring-shaped chains. Quantum chemical calculations on the cages, rings, and the experimentally known allotropes of arsenic suggest the nanostructures to be thermodynamically stable. The icosahedral cages are modifications of the gray allotrope of arsenic, while the ring-shaped chains are structurally related to the red allotrope of phosphorus. Comparisons between the analogous allotropes of arsenic and phosphorus show distinct differences. While phosphorus favors the ring-shaped chains over the icosahedral cages, large cages become favorable for arsenic. From the thermodynamical point of view, experimental preparation of the proposed families of arsenic nanostructures is expected to be viable.

Computational NMR Spectroscopy of Organoarsenicals and the Natural Polyarsenic Compound Arsenicin A

“…Current capabilities for predicting NMR spectra therefore virtually encompass the whole Periodic Table. Computations on arsenic clusters and rings have revealed a variety of fascinating motifs. [23,24] Hence, we believe the computational elucidation of the structure of arsenicin A (1) to be a valuable contribution to understanding the chemistry and NMR spectroscopy of an emerging class of intriguing natural substances such as organoarsenicals. Arsenicin A is also interesting from a computational viewpoint, since it is a relatively small and nonpolar molecule but contains a set of fairly heavy As atoms.…”

Theoretical Investigation of Clusters of Phosphorus and Arsenic: Fascination and Temptation of High Symmetries

“…The great stability of these curved C 2v -symmetric structures was discovered by Häser, and they were also treated by Karttunen et al for P 18 up to P 78 . [19] By carrying out a ring closure [19,20] one gets X 10n with D nh symmetry ( Figure 1). These rings are without strain around X 180 , as can be inferred from corresponding angles of the curved C 2v chains, whereas some strain is inevitable below and above that size.…”

“…Karttunen et al [19,20] have recently applied theoretical methods for I h -symmetric clusters as large as As 500 and P 720 , and ring-shaped clusters X 10n (X = P, As) with symmetry D nh up to X 360 . Dodecahedral P 20 was long ago computed to be unstable with respect to tetrahedral P 4 , [12] more recent work reaches the same conclusion for fullerene-like clusters P m , for m between 14 and 60.…”

“…This was accomplished by applying a genetic algorithm. P 20 and As 20 are just small enough for such a procedure to be feasible; they are also large enough to test Häsers structural rules and the usefulness of the genetic algorithm.…”

“…[14,36] The more CPU-demanding calculations for clusters with over 50 atoms were done with parallel implementations for SCF, [5] B3LYP, [33] and RI-MP2 (module RICC2) [15] on typically eight processors. A genetic algorithm [31] was employed to find low-energy structures for P 20 and As 20 . The population size was 40, the number of children 32.…”