Shinji Muramatsu

Energy gap of nanoscale Si rods

The electronic structure of silicon rods has been studied by means of the tight‐binding recursion method to investigate the dependence of the energy gap (Eg) on a rod length and the direction of the rod axis. An empirical expression for Eg is derived from numerical results for the rods in 〈100〉, 〈110〉, and 〈111〉 directions. This expression is applicable to the energy gaps of wires and crystallites, which can be regarded as limiting cases of rods.

X‐ray absorption near‐edge structure of complex compounds (NH4)3RhCl6, K3RuCl6, and Ru(NH3)6Cl3

X‐ray absorption spectra of chlorine K edge, ruthenium LIII edge, and rhodium LIII edge from (NH4)3[RhCl6], K3[RuCl6], and [Ru(NH3)6]Cl3 have been measured with a Johann‐type 50 cm bent crystal vacuum spectrograph. The white lines due to the transitions to the incompletely filled antibonding molecular orbital (MO) 2t2g(π*) or nonbonding orbital t2g and the empty antibonding MO 3eg(σ*) for the octahedral complexes have been observed in the Cl K edge, Ru LIII edge, and Rh LIII edge regions. It is found that the two absorption peaks at the Ru LIII edge reflect the ligand‐field effect. An interpretation for experimental results of the Cl K edge and the Ru LIII edge absorption spectra in K3RuCl6 on the basis of the MO scheme leads us to the conclusion that the white lines at the Cl K edge suffer from the effect of core hole.

Sulfur-K X-Ray Spectra and Electronic Structure of a Semiconductor Ag2S

The Kβ emission and K-absorption spectra of sulfur in Ag2S are carefully measured and compared with the sulfur Kβ emission and K-absorption spectra of Cu1.8S reported previously. The spectra of Ag2S clearly show the existence of the energy gap in semiconducting Ag2S in contrast to the metallic phase Cu1.8S where the Kβ band edge overlaps with the K absorption edge. The sulfur-Kβ emission spectrum of Ag2S consists of two prominent peaks. The intensity of the high-energy peak is much greater than that of the low-energy peak, contrary to the sulfur-Kβ emission spectrum of Cu1.8S. It is suggested that the bottom of the conduction band of Ag2S arises mainly from the sulfur 4p states.

Palladium Liii x‐ray absorption‐edge structures of K2PdCl6, K2PdCl4, (NH4)2PdCl4, and trans‐[Pd(NH3)2Cl2]

The palladium Liii absorption spectra of complex compounds K2PdCl6, K2PdCl4, (NH4)2PdCl4, and trans‐[Pd(NH3)2Cl2] have been measured with a 50 cm bent‐quartz crystal vacuum spectrograph. A strong ‘‘white line’’ has been found at the absorption threshold and a few weak structures have been observed in the energy range of about 20 eV above the white line. These absorption structures have been interpreted in terms of molecular‐orbital (MO) theory. The Pd Liii absorption spectrum of trans‐[Pd(NH3)2Cl2] is somewhat different from those of K2PdCl4 and (NH4)2PdCl4 which are quite alike. The white line of K2PdCl6 shifts by 2.0 eV toward higher energies relative to that of K2PdCl4 or (NH4)2PdCl4. This chemical shift is due to the difference of the oxidation states of the palladium ions Pd2+ and Pd4+.

Chirality-dependence of energy gaps of semiconducting nanotubules

Abstract The energy gap of semiconducting graphitic tubules with radius R and chiral angle θ is studied from an analytical approach based on the tight-binding approximation, to find out its dependence on their chirality. It is found that the energy gap has a part proportional to cos(3θ) R 2 , in agreement with our recent prediction deduced from a numerical investigation.

Simple expressions for elastic constants c11, c12, and c44 and internal displacements of semiconductors

Simple expressions are given for elastic stiffness constants c 11, c 12, and c 44 and Kleinman’s internal displacement parameter ζ. They all are represented by the bulk modulus and covalency alone, and predict fairly well the experimental results. These expressions are useful for getting a simple estimate of ζ as well as c 11, c 12, and c 44.

Chlorine K x‐ray absorption spectra from CrCl3 ⋅ 6H2O and FeCl3 ⋅ 6H2O

Chlorine K x‐ray absorption spectra are reported in CrCl3 ⋅ 6H20 and FeCl3 ⋅ 6H20 crystals. A new feature in the Crd3 ⋅ 6H20 spectrum the splitting of 3d levels of Cr3+ ion in the crystal field of CrCl3 ⋅ 6H20. The white lines in the spectra are discussed. (AIP)

Influence of ligands on the x‐ray absorption near‐edge structure of palladium(II) complex compounds

The palladium LIII absorption and chlorine K absorption spectra from [Pd(NH3)4]Cl2 ⋅ H2O and Pd(OCOCH3)2 have been reported for the first time and discussed in connection with the Pd LIII absorption and Cl K absorption spectra of K2PdCl4, reported previously. The influence of the ligands Cl−, OCOCH−3, and NH3 has been observed in the pallaldium LIII absorption spectra of these compounds. The observed chemical shift of a strong ‘‘white line’’ at the Pd LIII absorption threshold can be explained in terms of the spectrochemical series of the ligands. An intense white line disappears at the Cl K absorption threshold of [Pd(NH3)4]Cl2 ⋅ H2O in contrast to the Cl K absorption spectrum of K2PdCl4.

Multiple-scattering calculation of sulfur K x-ray absorption spectra for FeS, CoS and NiS

Abstract Sulfur K X-ray-absorption near-edge-structures (XANES) are calculated for the first time for NiAs-type FeS, CoS and NiS crystals having a hexagonal structure from a multiple-scattering approach within a muffin-tin approximation. Comparison between the calculated and experimental results indicates that a core hole created in the absorbing S atom does not so strongly affect the S K XANES of the metallic phase FeS, CoS and NiS.

X-ray-absorption near-edge-structure study of diamond: A multiple-scattering approach

Abstract The X-ray absorption near-edge structure (XANES) on diamond has been studied for the first time from a multiple-scattering (MS) approach in the framework of muffin-tin approximation. The general feature of an experimental K -XANES spectrum except for the first peak is accounted for by the MS approach containing a self-consistent-field (SCF) calculation to take into account the effect of core holes. The origin of the missing of the first peak is discussed.