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In this work, a comprehensive study on the influences of the various synthesizing parameters of monoclinic Cu2SnS3 using the RF sputtering method, followed by the sulfurization process, is investigated. In particular, the impact of sputtering power and pressure on multi-material target Cu–Sn (compositional ratio Cu:Sn of 52:48%) was examined. All samples exhibited a monoclinic structure with similar split bandgaps around 0.9 eV. Increasing sputtering power showed direct effects on the sputtered Cu/Sn atoms ratio and the secondary phases obtained. The increase of sputtering pressure causes gas droplets and blistering on the film surfaces. The effects of changing the sulfurization temperature and the sulfur powder amount were also studied. The increase in the sulfurization temperature reduces the surface roughness, increases film crystallinity, and minimizes Cu-based secondary phases. The sulfur amount used during the sulfurization process showed a vital impact on film formation. Using a small amount of sulfur produced a partially sulfurized film that exhibited a poor performance solar cell. A power conversion efficiency of 1.94% is achieved with the optimized condition for the bare Cu2SnS3 without doping or heat treatment for the fabricated cell. [ABSTRACT FROM AUTHOR]

A complete set of low temperature elastic constants Cij and piezoelectric coefficients eij of α-quartz single crystal has been investigated by resonance ultrasound spectroscopy coupled with a laser-Doppler interferometry. Most elastic constants showed monotonic elastic stiffening, while C66 continuously softened as the temperature decreased. Two piezoelectric coefficients eij showed monotonic decreasing upon cooling, and we found a strong correlation between e11 and C66, representing that thermal contraction induced internal strain plays an important role in their temperature behaviors. Group theoretical lattice dynamics analysis revealed that the elastic softening and the correlation can be attributed to an optical-mode-phonon-type internal strain having doubly degenerated E symmetry in the point group of D3. [ABSTRACT FROM AUTHOR]

We report first-principle electronic-state calculations for aluminum (Al) nanowires, which receive much attention as a new device material. First-principle calculations of the periodic boundary nanowire models have been carried out by means of supercell approximation techniques with density functional theory. The stable structures of Al nanowires have been investigated by geometry optimization of model structures of various types. For each stable structure, we have discussed the properties of nanowire in detail, such as radius of wire, interatomic distances, and stability for deformation. Furthermore, the growth and the reconstruction of nanowire by adsoprtion of Al atom have been simulated. We have also discussed the electronic processes and the driving forces in the growing process of Al nanowire, in terms of the quantum mechanical energy densities based on the regional density functional theory [Tachibana, J. Chem. Phys. 115, 3497 (2001)]. They have disclosed the driving force of the stability in electronic processes and give new images of microscopic electronic stresses. [ABSTRACT FROM AUTHOR]

We have carried out the MRCI ab initio calculations for small lithium and sodium clusters, and elucidate the interaction between atoms in various high-spin electronic states, in terms of the quantum mechanical energy densities based on the regional density functional theory [Tachibana, J. Chem. Phys. 115, 3497 (2001)]. When the separated two electronic drop regions, where the electronic kinetic-energy density is positive, connect to each other, it is observed that ratios of occupation on configurations change rapidly in the Li[sub 2] molecule. These results are considered as one of the evidences that valence electrons can move around both two Li atoms freely in the meaning of classical mechanics. The shape of electronic drop region depends strongly on the electronic state and represents the characteristics of interaction clearly, and the electronic tension density also gives new images of microscopic electronic stresses. Furthermore, we have clarified the most stable structures of Li[sub 3] and Li[sub 4] for the high-spin electronic state, which are respectively different from the most stable structures for the low-spin electronic state. The stabilization energy due to taking in a Li atom is raised gradually as the number of atoms in Li[sub n] cluster increases in the initial stage of cluster propagation. The formation energies of Na[sub 2], Na[sub 3], and Na[sub 4] clusters are much smaller than that of the corresponding lithium clusters. [ABSTRACT FROM AUTHOR]

Complete set of low temperature elastic constants and piezoelectric coefficients of [alpha]-quartz single crystal is examined by resonance ultrasound spectroscopy coupled with a laser-Doppler interferometry. The studies have shown that the elastic softening and the correlation are attributed to an optical-mode-phonon-type internal strain having doubly degenerated E symmetry in the point group of [D.sub.3].

The effect of manganese content (Mn-content) on the beta phase (β-phase) stability, plastic deformability and mechanical behavior of titanium and (8–18 wt.%) manganese low-cost alloys were investigated. The alloys were produced by electric-arc melting under inert argon atmosphere. Microstructure change during cold rolling was evaluated through x-ray diffraction, scanning electron microscope, transmission electron microscope and electron backscatter diffraction in solution-treated and cold-deformed conditions. The β-phase was predominant in all the alloys under study in addition to very fine ω-phase precipitates, especially in the lower Mn-content alloys. Cold workability of the alloys was initially increased in the low Mn-content alloys and then decreased dramatically in the higher Mn-content alloys. The deformation mechanisms were a combination between dislocation slipping and twinning, with a predominance of twinning in the low Mn-content and slipping in the high Mn-content alloys. Tensile test results showed that an ultra-high-strength alloy of about 1950 MPa was obtained in the high Mn-content alloys after cold deformation. [ABSTRACT FROM AUTHOR]