Molecular dynamics simulation of C60 encapsulated in boron nitride nanotubesMoon, Won Ha; Son, Myung Sik; Lee, Jun Ha; Hwang, Ho Jung
doi: 10.1002/pssb.200402032pmid: N/A
We investigate the C60 chain encapsulated in boron nitride (BN) nanotubes using molecular‐dynamics simulation. The most favorable BN nanotubes for encapsulation of C60 molecules are (10, 10) and (17, 0) with energy gains of 3.83 and 3.61 eV per C60 for (n, n) and (n, 0) BN nanotubes, respectively. For the diffusion of a C60 into the tube, the position of atoms of a C60 must be not located above the outer wall of the BN nanotube. The C60 located above the outer wall is quickly absorbed and moves on the surface of the tube. The C60 absorbed on the surface is not spontaneously encapsulated inside the tube, which is due to the energy barrier (0.48 eV) of the edge of the BN nanotube. We also calculate the energy barrier for drawing C60 outside the (10, 10) BN nanotube, which is above 3.92 eV. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The (CuGaSe2)1−x (MgSe)x alloy system (0 ≤ x ≤ 0.5): X‐ray diffraction, energy dispersive spectrometry and differential thermal analysisGrima Gallardo, P.; Muñoz, M.; Delgado, G. E.; Briceño, J. M.; Ruiz, J.
doi: 10.1002/pssb.200302010pmid: N/A
The (CuGaSe2)1−x(MgSe)x alloy system (0 < x ≤ 0.5) was investigated using X‐ray powder diffraction, energy dispersion spectrometry and differential thermal analysis. The solubility of MgSe in CuGaSe2 was found to be nearly complete for all the compositions studied, although traces of MgSe appear as a secondary phase at x ≥ 0.15. All the alloys showed the chalcopyrite structure and the lattice parameters of the unit cell do not follow a linear behavior but showed a soft local maximum at x ∼ 0.15. In the single‐phase field, the increasing behavior of the lattice parameters can be reproduced using an extension for quaternary alloys of Jaffe and Zunger's model for chalcopyrites. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preparation and characterization of (CuInSe2)1−x(CoSe)x alloys in the composition range 0 ≤ x ≤ 2/3Grima‐Gallardo, P.; Muñoz, M.; Ruiz, J.; Power, C.; González, J.; LeGodec, Y.; Munsch, P.; Itié, J. P.; Briceño, V.; Briceño, J. M.
doi: 10.1002/pssb.200402016pmid: N/A
Polycrystalline samples of (CuInSe2)1−x(CoSe)x alloys were prepared by the normal melt and anneal technique in the composition range 0 < x ≤ 2/3. The obtained ingots were characterized by scanning electron microscopy, X‐ray diffraction and differential thermal analysis techniques. A sample with x = 2/3 (prepared a posteriori) was also studied by the Raman shift technique. The results showed a complex behavior of the phase diagram. The phase (α) with chalcopyrite structure exists in a narrow interval 0 < x < 0.1 in the composition range; then, for 0.1 < x < 0.25, the ordered α phase gradually transforms into a disordered (α′) phase where the cation sites are multi‐occupied (Cu, Co and In) at random. For 0.25 < x < 0.35, two phases were observed, the α′ phase and another, not identified (γ) phase. Finally, for 0.35 < x < 2/3, another chalcopyrite‐like phase (α″) was observed together with traces of the γ phase. The sequence of phase transformations in the studied composition range seems to be α → α′ → α′ + γ → α″ + γ. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Relations for the high‐pressure melting temperature of alkali halides based on the diffusional driving force models: NaCl as an exampleFang, Zheng‐Hua
doi: 10.1002/pssb.200302017pmid: N/A
Two different diffusional driving force models were presented by Sharma et al. [Indian J. Pure Appl. Phys. 29, 637 (1991)] and Singh [J. Phys. Chem. Solids 63, 1935 (2002)], respectively, for estimating the zero‐pressure melting temperatures of alkali halides. Whether the two models are suitable for the analysis of the high‐pressure melting temperature of alkali halides is examined in this paper. It is shown that, supposing that the product of the thermal expansivity and the isothermal bulk modulus is inversely proportional to the volume along the melting curve, then the two diffusional force models are equivalent and the same relation for the high‐pressure melting temperature of solids may be derived. The reasonableness of this assumption is supported by the analysis and test on NaCl up to 1 Mbar, and is presented here. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Split and sealing of dislocated pipes at the front of a growing crystalGutkin, M. Yu.; Sheinerman, A. G.
doi: 10.1002/pssb.200302019pmid: N/A
A model is suggested for the split of dislocated pipes at the front a growing crystal. Within the model, the pipe split occurs through the generation of a dislocation semi‐loop at the pipe and crystal surfaces and its subsequent expansion into the crystal interior. The strain energy of such a dislocation semi‐loop as well as the stress field of a dislocated pipe perpendicular to a flat crystal surface are calculated. The parameter regions are determined at which the expansion of the dislocation semi‐loop is energetically favorable and, thus, the pipe split becomes irreversible. A mechanism is proposed for the formation of a stable semi‐loop resulting in the split and possible subsequent overgrowth of the dislocated pipe. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Charge‐ordering correlated elastic anomalies in Pr1−xCaxMnO3 perovskiteChen, C. X.; Qian, T.; Zheng, R. K.; Wang, F.; Li, X. G.
doi: 10.1002/pssb.200302023pmid: N/A
The temperature dependence of the elastic properties of polycrystalline manganite Pr1−xCaxMnO3 (0.5 ≤ x ≤ 0.85) has been studied systematically by means of ultrasonic measurements. It was found that the longitudinal modulus starts to soften obviously with decreasing temperature from higher temperature to the charge‐ordering transition temperature Tco, and stiffens dramatically just below Tco. The elastic anomalies observed near Tco cannot be explained based on a conventional antiferromagnetic transition. The electron–phonon coupling originating from the Jahn–Teller effect may play an important role in the system. The good fit of the theory to the temperature dependence of the elastic modulus data indicates that the mean‐field theory, which describes the coupling of Jahn–Teller ions to lattice distortions of the Jahn–Teller system, adequately characterizes the behavior. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fragmentation of multiply charged simple metal clusters in the liquid‐drop stabilized jellium modelPayami, M.
doi: 10.1002/pssb.200302029pmid: N/A
In this work, we have used the liquid‐drop model in the context of stabilized jellium model, to study the stability of Z‐ply charged (Z = 1, 2, 3, 4) metal clusters of different species against fragmentation. The liquid drop energy coefficients for each rs value are obtained from fitting of the self‐consistent Kohn‐Sham results for 0 ≤ N ≤ 100. The fission barriers are calculated using the two‐sphere model. Results show that the singly ionized clusters are stable against any spontaneous fragmentation. However, multiply charged clusters of sufficiently small sizes may undergo spontaneous decay via fission processes. The size at which competition between evaporation and fission starts, is predicted in good agreement with experiment for r ≥ 3.99. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron momentum density of hexagonal cadmium studied by Compton scatteringReniewicz, H.; Andrejczuk, A.; Brancewicz, M.; Żukowski, E.; Dobrzyński, L.; Kaprzyk, S.
doi: 10.1002/pssb.200302002pmid: N/A
The directional electron momentum density distributions (Compton profiles) of single‐crystal cadmium have been measured in transmission and reflection experimental geometries using high‐energy (662 keV) gamma radiation from a 137Cs isotope source. Profiles along the [100] and [110] directions in reciprocal space were measured in both geometries, whereas only the transmission geometry was used for the measurements along the [001] direction. The experimental data have been compared with corresponding theoretical KKR semi‐relativistic calculations. The directional difference profiles, both experimental and theoretical, show, similarly to other hexagonal systems, very small anisotropy of the electron momentum density in hexagonal cadmium, about 0.3%, i.e. less than half of that presented in the literature for cubic systems. Minor discrepancies between KKR calculations and experiment probably occur due to the necessity to introduce an anisotropic electron–electron correlation correction. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)