Ground state structures and properties of small hydrogenated silicon clusters

Abstract

We present results for ground state structures and properties of small hydrogenated silicon clusters using the Car-Parrinello molecular dynamics with simulated annealing. We discuss the nature of bonding of hydrogen in these clusters. We find that hydrogen can form a bridge like Si-H-Si bond connecting two silicon atoms. We find that in the case of a compact and closed silicon cluster hydrogen bonds to the silicon cluster from outside. To understand the structural evolutions and properties of silicon cluster due to hydrogenation, we have studied the cohesive energy and first excited electronic level gap of clusters as a function of hydrogenation. We find that first excited electronic level gap of Si n and Si n H fluctuates as function of size and this may provide a first principle basis for the short-range potential fluctuations in hydrogenated amorphous silicon. The stability of hydrogenated silicon clusters is also discussed.

Silicon Monohydride Clusters SinH (n = 4−10) and Their Anions: Structures, Thermochemistry, and Electron Affinities

“…For neutral Si 5 H, the structure of the ground state (shown in Figure a) displays C 2 υ symmetry with 2 B 2 electronic state at all five DFT methods. This result is different from the previous result reported by Prasad et al − They reported that the structure of the ground state of Si 5 H is the nonclassical H-bridged structure (shown in Figure b) at the CPMD, , NTBMD, and GAs 22,23 levels of theory. The structure of Figure b also has C 2 υ symmetry with a 2 B 1 or 2 A 1 electronic state.…”

“…In 1998, Neumark and co-workers 8 assigned the 2 A‘ state as the ground state of neutral Si 4 H by photoelectron spectroscopy experiments and MP2/6-31G* level of theory. Recently, Prasad et al − presented the groud-state structures for small Si n H (2 ≤ n ≤ 10) using the CPMD, NTBMD, and GAs methods.…”

“…During the past decade, silicon hydrides have attracted a lot of attention because of their potential applications in semiconductors, optoelectronics, and surface growth processes and because of their likely existence in the circumstellar atmospheres of evolved carbon stars. − The binary clusters of silicon and hydrogen play key roles in the chemical vapor deposition of thin films, photoluminescence of porous silicon, potential fluctuations, and the Staebler-Wronski effect of hydrogenated amorphous silicon (α-Si:H), which is an important but poorly understood process. − Knowledge of the ground and low-lying electronic states of neutral and anionic silicon hydride clusters is very important for understanding these processes. With this motivation, we have carried out a detailed study of the structures, thermochemistry, and electron affinities of silicon monohydride clusters and their anions using density functional theory (DFT). − …”

Global Optimization of Atomic Cluster Structures Using Parallel Genetic Algorithms

“…[18] clearly demonstrate that our MGAC/CPMD approach is able to find new, previously unknown, structures with significant lower energy than those previously reported by other authors [21][22][23][24][25][26]. The results in Ref .…”

Structure and Charge States of the Selected Hydrogenated Silicon Clusters Si2-Si8 by Non-Conventional Tight-Binding Method

“…Computer simulation of ground states of small pure [5][6][7][8][9] and hydrogenated [10][11][12] silicon clusters were studied in many works. Many of these results were confirmed by high-resolution ion mobility measurements [13][14], absorption spectroscopy [15], ion mass spectrometry and light scattering [16].…”