Hafnium tantalum sulfide (Hf10Ta3S3), a new structure type related to .gamma.-brass: confirmation of Hume-Rothery and Brewer-Engel electron concentration rules

1993 ◽  
Vol 115 (14) ◽  
pp. 6126-6130 ◽  
Author(s):  
Gregory A. Marking ◽  
Hugo F. Franzen
Keyword(s):  
Electron Concentration ◽  
Structure Type ◽  
Tantalum Sulfide

The Ir3Ge7 (D8f) Structure: an Electron Phase Related to γ-Brass

1996 ◽  
Vol 453 ◽  
Author(s):  
D. Swenson
Keyword(s):  
Electron Concentration ◽  
Structure Type ◽  
Large Concentration ◽  
Crystal Chemical ◽  
Formula Unit

AbstractThe crystallographic similarity between the Ir3Ge7 (D8f) and γ-brass (Cu5Zn8, D82) structures is discussed. By considering all phases known to possess the Ir3Ge7 structure, it is shown that phases of this structure type obey essentially the same electron concentration rules as does γ-brass, possessing on average 22 atoms/formula unit. Based on crystal-chemical considerations, it is further suggested that the Ir3Ge7 structure may be considered to be a structural derivative of γ-brass, in which 12 atoms have dropped out of the γ-brass lattice and the remaining atoms have undergone a certain amount of rearrangement in order to accommodate such a large concentration of vacancies. Finally, as further support of this idea, the phase NiGa4 is presented as an example of another γ-brass derived structure which contains crystallographic features of both γ-brass and the Ir3Ge7 structure.

Structure and Thermoelectric Properties of New Quaternary Tin and Lead Bismuth Selenides, K1+xM4-2xBi7+xSe15 (M = Sn, Pb) and K1+xSn5-xBi11+xSe22

2000 ◽  
Vol 626 ◽  
Author(s):  
Antje Mrotzek ◽  
Kyoung-Shin Choi ◽  
Duck-Young Chung ◽  
Melissa A. Lane ◽  
John R. Ireland ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Single Crystal ◽  
Thermoelectric Properties ◽  
Three Dimensional ◽  
Structure Type ◽  
Narrow Gap ◽  
Low Thermal Conductivity ◽  
Seebeck Coefficients ◽  
Metal Atoms ◽  
Anionic Framework

ABSTRACTWe present the structure and thermoelectric properties of the new quaternary selenides K1+xM4–2xBi7+xSe15 (M = Sn, Pb) and K1-xSn5-xBi11+xSe22. The compounds K1+xM4-2xBi7+xSe15 (M= Sn, Pb) crystallize isostructural to A1+xPb4-2xSb7+xSe15 with A = K, Rb, while K1-xSn5-xBi11+xSe22 reveals a new structure type. In both structure types fragments of the Bi2Te3-type and the NaCl-type are connected to a three-dimensional anionic framework with K+ ions filled tunnels. The two structures vary by the size of the NaCl-type rods and are closely related to β-K2Bi8Se13 and K2.5Bi8.5Se14. The thermoelectric properties of K1+xM4-2xBi7+xSe15 (M = Sn, Pb) and K1-xSn5-xBi11+xSe22 were explored on single crystal and ingot samples. These compounds are narrow gap semiconductors and show n-type behavior with moderate Seebeck coefficients. They have very low thermal conductivity due to an extensive disorder of the metal atoms and possible “rattling” K+ ions.

A New Condition of Formation and Stablity of All Crystalline Systems in a Good Agreement with Experimental Data

2015 ◽  
Vol 11 (3) ◽  
pp. 3224-3228
Author(s):  
Tarek El-Ashram
Keyword(s):  
Experimental Data ◽  
Brillouin Zone ◽  
Electron Concentration ◽  
Free Electron ◽  
Lattice Point ◽  
Valence Electron ◽  
Fermi Gas ◽  
Valence Electron Concentration ◽  
Fermi Sphere ◽  
Good Agreement

In this paper we derived a new condition of formation and stability of all crystalline systems and we checked its validity andit is found to be in a good agreement with experimental data. This condition is derived directly from the quantum conditionson the free electron Fermi gas inside the crystal. The new condition relates both the volume of Fermi sphere VF andvolume of Brillouin zone VB by the valence electron concentration VEC as ;𝑽𝑭𝑽𝑩= 𝒏𝑽𝑬𝑪𝟐for all crystalline systems (wheren is the number of atoms per lattice point).

Site preference and atomic ordering in the ternary Rh5Ga2As: first-principles calculations

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Nilanjan Roy ◽  
Sucharita Giri ◽  
Harshit ◽  
Partha P. Jana
Keyword(s):  
Total Energy ◽  
First Principles ◽  
Density Functional ◽  
Structure Type ◽  
Site Preference ◽  
X Ray Diffraction ◽  
Atomic Ordering ◽  
Functional Theory ◽  
The Stability ◽  
Bonding Characteristics

Abstract The site preference and atomic ordering of the ternary Rh5Ga2As have been investigated using first-principles density functional theory (DFT). An interesting atomic ordering of two neighboring elements Ga and As reported in the structure of Rh5Ga2As by X-ray diffraction data only is confirmed by first-principles total-energy calculations. The previously reported experimental model with Ga/As ordering is indeed the most stable in the structure of Rh5Ga2As. The calculation detected that there is an obvious trend concerning the influence of the heteroatomic Rh–Ga/As contacts on the calculated total energy. Interestingly, the orderly distribution of As and Ga that is found in the binary GaAs (Zinc-blende structure type), retained to ternary Rh5Ga2As. The density of states (DOS) and Crystal Orbital Hamiltonian Population (COHP) are calculated to enlighten the stability and bonding characteristics in the structure of Rh5Ga2As. The bonding analysis also confirms that Rh–Ga/As short contacts are the major driving force towards the overall stability of the compound.

An1.33T4Al8Si2 (An = Ce, Th, U, Np; T = Ni, Co): Actinide Intermetallics with Disordered Gd1+xFe4Si10–y Structure Type Grown from Metal Flux

2021 ◽  
Author(s):  
Ashini S. Jayasinghe ◽  
You Lai ◽  
Wesley M. Potter ◽  
Cory J. Windorff ◽  
Ryan Baumbach ◽  
...  
Keyword(s):  
Structure Type ◽  
Metal Flux

scholarly journals Analysis of Flexural Vibrations of a Piezoelectric Semiconductor Nanoplate Driven by a Time-Harmonic Force

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3926
Author(s):  
Mengen Li ◽  
Qiaoyun Zhang ◽  
Bingbing Wang ◽  
Minghao Zhao
Keyword(s):  
Electron Concentration ◽  
Smart Devices ◽  
Harmonic Force ◽  
Plate Structures ◽  
Piezoelectric Semiconductor ◽  
Initial Electron ◽  
Time Harmonic ◽  
Semiconductor Plate ◽  
Flexural Vibrations ◽  
Piezoelectric Semiconductors

The performance of devices fabricated from piezoelectric semiconductors, such as sensors and actuators in microelectromechanical systems, is superior; furthermore, plate structures are the core components of these smart devices. It is thus important to analyze the electromechanical coupling properties of piezoelectric semiconductor nanoplates. We established a nanoplate model for the piezoelectric semiconductor plate structure by extending the first-order shear deformation theory. The flexural vibrations of nanoplates subjected to a transversely time-harmonic force were investigated. The vibrational modes and natural frequencies were obtained by using the matrix eigenvalue solver in COMSOL Multiphysics 5.3a, and the convergence analysis was carried out to guarantee accurate results. In numerical cases, the tuning effect of the initial electron concentration on mechanics and electric properties is deeply discussed. The numerical results show that the initial electron concentration greatly affects the natural frequency and electromechanical fields of piezoelectric semiconductors, and a high initial electron concentration can reduce the electromechanical fields and the stiffness of piezoelectric semiconductors due to the electron screening effect. We analyzed the flexural vibration of typical piezoelectric semiconductor plate structures, which provide theoretical guidance for the development of new piezotronic devices.

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