Structures and physical properties of ∊-FeSi-type and CsCl-type RuSi studied by first-principles pseudopotential calculations

2000 ◽  
Vol 56 (3) ◽  
pp. 369-376 ◽  
Author(s):  
Lidunka Vočadlo ◽  
Geoffrey D. Price ◽  
I. G. Wood
Keyword(s):  
High Pressure ◽  
First Principles ◽  
Stable Phase ◽  
Band Structure Calculations ◽  
Pseudopotential Calculations ◽  
Cscl Type ◽  
Logarithmic Equation ◽  
Structure Calculations ◽  
Cell Volumes ◽  
Good Agreement

An investigation of the relative stability of the two known polymorphs of RuSi, having the ∊-FeSi and CsCl structures, has been made by first-principles pseudopotential calculations. The resulting cell volumes and fractional coordinates at P = 0 are in good agreement with experiment. Application of high pressure to the ∊-FeSi phase of RuSi is predicted to produce a structure having almost perfect sevenfold coordination. However, it appears that RuSi having the CsCl-type structure will be the thermodynamically most stable phase for pressures greater than 3.6 GPa. Fitting of the calculated internal energy versus volume to a fourth-order logarithmic equation of state led to values (at T = 0 K) for the bulk modulus, K 0, of 202 and 244 GPa for the ∊-FeSi and CsCl phases, respectively, in excellent agreement with experiment. Band-structure calculations for both phases are also presented.

Crystal structure, compressibility and possible phase transitions in \boldvarepsilon-FeSi studied by first-principles pseudopotential calculations

1999 ◽  
Vol 55 (4) ◽  
pp. 484-493 ◽  
Author(s):  
Lidunka Vočadlo ◽  
Geoffrey D. Price ◽  
I. G. Wood
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Phase Transitions ◽  
First Principles ◽  
Stable Phase ◽  
Third Order ◽  
First Derivative ◽  
Pseudopotential Calculations ◽  
Cscl Type ◽  
Murnaghan Equation

An investigation of the relative stability of the FeSi structure and of some hypothetical polymorphs of FeSi has been made by first-principles pseudopotential calculations. It has been shown that the observed distortion from ideal sevenfold coordination is essential in stabilizing the FeSi structure relative to one of the CsCl type. Application of high pressure to FeSi is predicted to produce a structure having nearly perfect sevenfold coordination. However, it appears that FeSi having a CsCl-type structure will be the thermodynamically most stable phase for pressures greater than 13 GPa. Fitting of the calculated internal energy vs volume for the FeSi structure to a third-order Birch–Murnaghan equation of state led to values, at T = 0 K, for the bulk modulus, K 0, and for its first derivative with respect to pressure, K 0′, of 227 GPa and 3.9, respectively.

Stacking Faults and 3C Quantum Wells in Hexagonal SiC Polytypes

2006 ◽  
Vol 527-529 ◽  
pp. 351-354 ◽  
Author(s):  
M.S. Miao ◽  
Walter R.L. Lambrecht
Keyword(s):  
Band Structure ◽  
Quantum Wells ◽  
First Principles ◽  
Driving Force ◽  
Stacking Faults ◽  
Band Gaps ◽  
Partial Dislocations ◽  
Band Structure Calculations ◽  
Thermodynamic Driving Force ◽  
Structure Calculations

The electronic driving force for growth of stacking faults (SF) in n-type 4H SiC under annealing and in operating devices is discussed. This involves two separate aspects: an overall thermodynamic driving force due to the capture of electrons in interface states and the barriers that need to be overcome to create dislocation kinks which advance the motion of partial dislocations and hence expansion of SF. The second problem studied in this paper is whether 3C SiC quantum wells in 4H SiC can have band gaps lower than 3C SiC. First-principles band structure calculations show that this is not the case due to the intrinsic screening of the spontaneous polarization fields.

The thermodynamic stability of three near-degenerate phases of platinum dioxide

2004 ◽  
Vol 848 ◽  
Author(s):  
Shuping Zhuo ◽  
Karl Sohlberg
Keyword(s):  
High Pressure ◽  
Fixed Point ◽  
Low Temperature ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Energy Surface ◽  
Stable Phase ◽  
Free Energies ◽  
Rutile Structure ◽  
Unstable Fixed Point

ABSTRACTThe thermodynamic stability of the three nearly energy degenerate crystal structures of PtO2 is studied here with first-principles-based calculations of their free energies. For P = 0 the α-(CdI2) structure is the thermodynamically stable phase at low temperature, while the β-(CaCl2) structure is stable at high pressure. The β'-(rutile) structure represents an unstable fixed point on the potential energy surface, or is possibly just barely bound. These results reconcile seemingly contradictory findings and answer longstanding questions about PtO2.

Specific Peculiarities of the Electronic Structure of SrPb3Br8 As Evidenced from First-Principles DFT Band-Structure Calculations

2019 ◽  
Vol 48 (5) ◽  
pp. 3059-3068 ◽  
Author(s):  
O. Y. Khyzhun ◽  
V. L. Bekenev ◽  
N. M. Denysyuk ◽  
L. I. Isaenko ◽  
A. P. Yelisseyev ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
First Principles ◽  
Band Structure Calculations ◽  
Structure Calculations

First-Principles Study of Structural and Vibrational Properties of α-SiO2 under Pressure

2015 ◽  
Vol 775 ◽  
pp. 191-196
Author(s):  
Xiao Wei Lei ◽  
Yong Song ◽  
Kuo Yang ◽  
Hui Zhao
Keyword(s):  
High Pressure ◽  
Perturbation Theory ◽  
Infrared Spectra ◽  
First Principles ◽  
Linear Response ◽  
Density Functional ◽  
Vibrational Properties ◽  
Vibrational Modes ◽  
Density Functional Perturbation Theory ◽  
Good Agreement

Using first principles approach, we present the structural, vibrational and dielectric properties of α-SiO2. The calculations have been carried out within the density functional perturbation theory and linear response formalism using the norm-concerving pseudopotentials and a plane wave basis. All the vibrational modes identified are in good agreement with experiment. The calculated infrared spectra are also in good agreement with available experimental results both for the positions and the intensities of the main peaks. We find that the modes Eu7 and A2u4 splits in two respectively at high hydrostaticpressures. Then we calculate the infrared spectra under high pressure of different orientations. The vibrational modes in different phase transitions are reported and discussed respectively.

The temperature dependence of the resistivity of ferromagnetic metals

1961 ◽  
Vol 263 (1315) ◽  
pp. 473-482 ◽  
Keyword(s):  
Band Structure ◽  
Temperature Dependence ◽  
Fourth Power ◽  
Fractional Change ◽  
Ferromagnetic Metals ◽  
Band Structure Calculations ◽  
Structure Calculations ◽  
Good Agreement

The temperature dependence of the resistivity of nickel and gadolinium has been measured. For nickel, the results are in good agreement with the band-structure calculations of Fletcher (1952); for gadolinium the fractional change in resistivity is almost exactly equal to the fourth power of the reduced magnetization.

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