Optical Properties and Quasiparticle Band Gaps of Transition-Metal Atoms Encapsulated by Silicon Cages

Abstract

Semiconductors assembled upon nano-templates consisting of metalencapsulating Si cage clusters (M@Sin) have been proposed as prospective materials for nano-devices. To make an accurate and systematic prediction of the optical properties of such M@Sin clusters, which represent a new type of metal-silicon hybrid material for components in nanoelectronics, we have performed first-principles calculations of the electronic properties and quasiparticle band gaps for a variety of M@Si12 (M = Ti, Cr, Zr, Mo, Ru, Pd, Hf, and Os) and M@Si16 (M = Ti, Zr, and Hf) clusters. At first stage, the electronic structure calculations have been performed within plane-wave density functional theory in order to predict equilibrium geometries, polarizabilities, and optical absorption spectra of these endohedral cage-like clusters. The quasiparticle calculations were performed within the GW approximation, which predict that all these systems are semiconductors exhibiting large band gaps. The present results have demonstrated that the independentparticle absorption spectra of M@Sin, calculated within the local density or generalized gradient approximations to density-functional theory, are dramatically influenced by manybody effects. On average, the quasiparticle band gaps were significantly increased, in comparison with the independent-particle gaps, giving values in the 2.45-5.64 eV range. Consequently, the inclusion of many-body effects in the electron-electron interaction, and going beyond the mean-field approximation of independent particles, might be essential to realistically describe the optical spectra of isolated M@Sin clusters, as well as their clusterassembled materials.

Germanium-based superatom clusters as excess electron compounds with significant static and dynamic NLO response; a DFT study

“…40 The literature reveals that only conventional types of superalkali clusters are explored for optical and nonlinear optical studies however several models can be efficiently utilized to be used as nonlinear optical responses. Literature also reveals, there are several superatom clusters (silicon-based) encapsulated by transition metals which were also studied for optical and magnetic excitation 41,42 Zintl polyanions, discovered by Eduard zintl in 1930 belong to the group (14,15) and show excellent physicochemical stability. 43 It is previously reported that zintl P 7 3À anion as core material can be used to design organo-zintl superalkali clusters which contain superb electron properties.…”

DFT/TDDFT study of electronic and optical properties of Surface-passivated Silicon nanocrystals, Sin (n = 20, 24, 26 and 28)

“…TDDFT calculations were performed with no symmetry constraints. A very similar approach has been used in a recent TDDFT study on silicon-based clusters [63].…”

Electronic Structure and High Magnetic Properties of (Cr, Co)-codoped 4H–SiC Studied by First-Principle Calculations

“…It is shown that if the impurities have a limited local magnetic moment, it is possible to generate magnetism in the matrix material. Some related modeling work [27,28] using first principles not only extends the scope of DFT methods for silicon-based systems containing transition metal atoms, but also demonstrates the feasibility of predictions made at the level of similar theoretical approaches. As far as we know, theoretical studies on the magnetic properties of SiC-base wide band-gap semiconductors doped with Cr and Co atoms are relatively rare.…”