Abstract
The electron-deficient nature of boron endows isolated boron clusters with a variety of interesting structural and bonding properties that can be further enriched through metal doping. In the current work, we report the structural and electronic properties of a series of chromium-doped boron clusters. The global minimum structures for CrBn clusters with an even number of n ranging from 8 to 22 are proposed through extensive first-principles swarm-intelligence structure searches. Half-sandwich structures are found to be preferred for CrB8, CrB10, CrB12 and CrB14 clusters and to transform to a drum-like structure at CrB16 cluster. Endohedral cage structures with the Cr atom located at the center are energetically most favorable for CrB20 and CrB22 clusters. Notably, the endohedral CrB20 cage has a high symmetry of D2d and a large HOMO–LUMO gap of 4.38 eV, whose stability is attributed to geometric fit and formation of an 18-electron closed-shell configuration. The current results advance our understanding of the structure and bonding of metal-doped boron clusters.
Highlights
IntroductionMotif.2 1D nanotubes[3,4,5] and 2D sheets[6,7,8] have been fabricated in which triangular planar B lattices with hexagonal holes are found to be energetically favorable.[9]
Boron is an element of fascinating structural and chemical complexity, leading to topics of considerable interest in chemistry
Other low-lying isomers are shown in the Electronic supplementary information (ESI), Fig. S1–S8.† Generally, the effect of Cr doping on the structures of B clusters gradually is enhanced as the number of B atoms increases
Summary
Motif.2 1D nanotubes[3,4,5] and 2D sheets[6,7,8] have been fabricated in which triangular planar B lattices with hexagonal holes are found to be energetically favorable.[9]. For larger B clusters, recent theoretical studies have suggested quasi-planar,[22,23] tubular,[24] cage-like[25] and bilayered[23] structures as ground states at certain sizes, and core–shell structures are generally expected to be energetically most favorable for n > $68.26–28. A theoretical study found that even the small B12 cluster can show interesting transitions from quasi-planar to tubular and cage-like structures through interactions with lithium atoms, in which charge transfer plays a critical role.[37]. Ground-state structures are proposed for CrBn clusters with an even number of n ranging from 8 to 22, revealing an intriguing transition from half-sandwich to drumlike and endohedral cage-like structures.
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