SURFACE PHONONS OF THE (100) SURFACE OF SOME COMPOUNDS WITH A ROCK-SALT CRYSTAL STRUCTURE

1991 ◽  
Vol 05 (05) ◽  
pp. 381-389 ◽  
Author(s):  
CHUHEI OSHIMA
Keyword(s):  
Crystal Structure ◽  
Rock Salt ◽  
Dispersion Curves ◽  
Shielding Effect ◽  
Transition Metal Carbide ◽  
Free Electrons ◽  
Salt Crystal ◽  
Dynamical Parameters ◽  
Surface Phonons ◽  
Electron Energy Loss

The energy dispersion curves of surface phonons of the (100) surface of some compounds with a rock-salt crystal structure (TiC, ZrC, HfC, NbC, TaC, MgO, and NiO) have been investigated using electron energy loss spectroscopy. Drastic changes in force constants on all the carbide surfaces are correlated with a rippled structure. On the other hand, the surface phonons of insulating compounds, NiO and MgO (100), have showed dispersion curves agreeing with the predicted ones calculated on the basis of a shell model with bulk dynamical parameters. No changes in the parameters near the NiO and MgO (100) surfaces have been detected. The shielding effect of free electrons on the surface phonon for the transition metal carbide surfaces is discussed.

scholarly journals Carrier concentration dependence of structural disorder in thermoelectric Sn1−xTe

IUCrJ ◽  
2016 ◽  
Vol 3 (5) ◽  
pp. 377-388 ◽  
Author(s):  
Mattia Sist ◽  
Ellen Marie Jensen Hedegaard ◽  
Sebastian Christensen ◽  
Niels Bindzus ◽  
Karl Frederik Færch Fischer ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Rock Salt ◽  
Theoretical Calculations ◽  
Rhombohedral Phase ◽  
Structural Disorder ◽  
Entropy Method ◽  
Salt Crystal ◽  
X Ray ◽  
Two Samples

SnTe is a promising thermoelectric and topological insulator material. Here, the presumably simple rock salt crystal structure of SnTe is studied comprehensively by means of high-resolution synchrotron single-crystal and powder X-ray diffraction from 20 to 800 K. Two samples with different carrier concentrations (sampleA= high, sampleB= low) have remarkably different atomic displacement parameters, especially at low temperatures. Both samples contain significant numbers of cation vacancies (1–2%) and ordering of Sn vacancies possibly occurs on warming, as corroborated by the appearance of multiple phases and strain above 400 K. The possible presence of disorder and anharmonicity is investigated in view of the low thermal conductivity of SnTe. Refinement of anharmonic Gram–Charlier parameters reveals marginal anharmonicity for sampleA, whereas sampleBexhibits anharmonic effects even at low temperature. For both samples, no indications are found of a low-temperature rhombohedral phase. Maximum entropy method (MEM) calculations are carried out, including nuclear-weighted X-ray MEM calculations (NXMEM). The atomic electron densities are spherical for sampleA, whereas for sampleBthe Te electron density is elongated along the 〈100〉 direction, with the maximum being displaced from the lattice position at higher temperatures. Overall, the crystal structure of SnTe is found to be defective and sample-dependent, and therefore theoretical calculations of perfect rock salt structures are not expected to predict the properties of real materials.

Investigations of the disorder in the TaxN thin films: On the first order Raman spectrum of the rock salt crystal structure

2013 ◽  
Vol 114 (4) ◽  
pp. 043707 ◽  
Author(s):  
M. Očko ◽  
S. Žonja ◽  
K. Salamon ◽  
M. Ivanda ◽  
L. Yu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Thin Films ◽  
Raman Spectrum ◽  
Rock Salt ◽  
Salt Crystal ◽  
First Order

scholarly journals Understanding the crystal structure-dependent electrochemical capacitance of spinel and rock-salt Ni–Co oxides via density function theory calculations

RSC Advances ◽  
2020 ◽  
Vol 10 (59) ◽  
pp. 35611-35618
Author(s):  
Xuan Sun ◽  
Jinfeng Sun ◽  
Lingzhi Guo ◽  
Linrui Hou ◽  
Changzhou Yuan
Keyword(s):  
Crystal Structure ◽  
Density Function ◽  
Rock Salt ◽  
Experimental Evaluation ◽  
Function Theory ◽  
Density Function Theory ◽  
Electrochemical Capacitance

The crystal structure dependent pseudocapacitance of binary spinel and rock-salt Ni–Co oxides is unveiled via the density function theory calculations, along with experimental evaluation.

Polysulfonylamine, CXXVIII [1]. Disulfonylamido-Gold(I)-Komplexe mit Tetrahydrothiophen als Ligand / Polysulfonylamines, CXXVIII. Disulfonylamido-gold(I) Complexes with Tetrahydrothiophene as Ligand

2000 ◽  
Vol 55 (9) ◽  
pp. 803-813 ◽  
Author(s):  
Birte Ahrens ◽  
Peter G. Jones
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Silver Salt ◽  
Solvent Free ◽  
Salt Crystal ◽  
Amide Ligands ◽  
Intermolecular Contacts ◽  
Independent Molecules

The molecular gold(I) complexes di(methanesulfonyl)amido-/V-(tetrahydrothiophene)gold(I) (1), di(p-chlorobenzenesulfonyl)amido-/V-(tetrahydrothiophene)gold(I) (2), and di(p-iodobenzenesulfonyl) amido-/V-(tetrahydrothiophene)gold(I) (3), were synthesised from (tetrahydrothiophene) chlorogold(I) and the appropriate silver salt. Crystal structure analyses were performed for all three compounds (3 both solvent-free and as a dichloromethane solvate 3a) and revealed a variety of intermolecular contacts. Compound 1 crystallizes with four independent molecules, two of which are connected by a gold-gold interaction of 3.2869(8) Å; several short nonclassical hydrogen bonds of the form C-H · O (the shortest with H · O 2.31 A) are observed. In compound 2, cyclodimers are formed via Au · Au contacts of 3.3302(8) Å; additionally Cl · Cl contacts of 3.457(3) Å are observed. Both forms of compound 3 are characterized by Au · I contacts, somewhat longer in 3 (3.6 - 4.3 Å) than in 3a (3.4 - 3.5 Å). The di(arenesulfonyl)amide ligands in 2, 3 and 3a display approximate C2 symmetry

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