scholarly journals Iron and sulfur isotope factors for pyrite from experimental gamma-resonant studies and heat capacity

2019 ◽  
Vol 64 (4) ◽  
pp. 372-386
Author(s):  
V. B. Polyakov ◽  
E. G. Osadchii ◽  
M. V. Voronin ◽  
V. O. Osadchii ◽  
L. V. Sipavina ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Kinetic Energy ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Temperature Dependence ◽  
Isotope Exchange ◽  
Resonant Scattering ◽  
Debye Model ◽  
Crystalline Lattice ◽  
Thermal Vibrations

Pyrite Moessbauer spectra (FeS2) is measured in the temperature range from 90 to 295 K. The temperature dependence of the isomer shift is described by the Debye model with Moessbauer temperature θM=551.4 K. Using these results, we calculated the kinetic energy of thermal vibrations of the iron sublattice of pyrite and the iron β-factor for pyrite: 103lnβ57Fe/54Fe=(1.2665±0.0391)x–(0.4584±0.0283) × 10-2x2+(0.2581±0.0239) × 10-4x3; x=106/T 2 (K-2) The Moessbauer-derived iron β-factor for pyrite agrees well with results of ab initio calculations, 57Fe nuclear inelastic γ-resonant scattering synchrotron experiments and direct isotope exchange experiments between pyrite and Fe2+ dissolved in water. Heat capacity of pyrite is measured at temperatures from 79 to 300 K. Its temperature dependence are described using the Thirring expansion. Based on this expansion, the kinetic energy of thermal vibrations of total crystalline lattice of pyrite is calculated. The kinetic energy of the thermal vibrations of the sulfur sublattice in pyrite is found by subtracting the iron sublattice kinetic energy from the total kinetic energy of pyrite crystalline lattice. Temperature dependence of 34S/32S β-factor for pyrite calculated from the kinetic energy of the sulfur sublattice is following: 103lnβ34Fe/32Fe=(1.7532±0.0623) x–(1.0470±0.0752) × 10-2 x2+(1.0424±0.1126) × 10-4 x3; x=106/T 2 (K-2) This 34S/32S β-factor values exhibit a good agreement with of ab initio calculations and isotope-exchange experimental results in the pyrite-sphalerite-galenite system.

Atomic thermal vibrations in semiconductors: Ab initio calculations and EXAFS measurements

1996 ◽  
Vol 219-220 ◽  
pp. 436-438 ◽  
Author(s):  
D. Strauch ◽  
P. Pavone ◽  
N. Nerb ◽  
K. Karch ◽  
W. Windl ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Thermal Vibrations

Crystal Structure of and ab initio Calculations on [(C6H5)(CH3)CH-NH]- P(O)(p-OC6H4CH3)2, Syntheses and Spectroscopic Characterization of N-Benzyl Phosphoramidic Acid (4-Methylphenyl)ester Derivatives

2005 ◽  
Vol 60 (1) ◽  
pp. 67-74 ◽  
Author(s):  
Khodayar Gholivand ◽  
Zahra Shariatinia ◽  
Mehrdad Pourayoubi
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Spectroscopic Characterization ◽  
Crystalline Lattice ◽  
Independent Molecule ◽  
Nmr Data ◽  
Independent Molecules

Some new N-benzyl phosphoramidic acid (4-methylphenyl)ester derivatives were synthesized and characterized by 1H, 13C, 31P NMR and IR spectroscopy and elemental analysis. The structure of [(C6H5)(CH3)CH-NH]P(O)(p-OC6H4CH3)2 (2) was investigated. This compound exists in polymeric zigzag chains in the crystalline lattice produced by hydrogen bonding built from two alternating independent molecules. NMR data indicate two diastereotopic p-cresol groups as confirmed by Xray crystallography. Ab initio calculations were performed on the geometry of compound 2 at the UHF/6-311G** and B3LYP/6-311G** levels. The optimized structure of each independent molecule contains two different p-cresol groups, in agreement with the experimental results.

scholarly journals Temperature dependence of decagonal quasicrystals heat capacity

2018 ◽  
Vol 26 (1) ◽  
pp. 35-38
Author(s):  
O. V. Sukhova ◽  
Yu. V. Syrovatko
Keyword(s):  
Heat Capacity ◽  
Temperature Dependence ◽  
Debye Temperature ◽  
Temperature Effects ◽  
Debye Model ◽  
Decagonal Quasicrystal ◽  
Excessive Heat ◽  
Ni Alloys ◽  
Decagonal Quasicrystals

The heat capacity of decagonal quasicrystals of the Al–Co–Cu or Al–Co–Ni alloys was calculated at the temperatures of 600, 700, and 900 K in this work. The expression for the heat capacity of the quasicrystals was obtained based on the Debye model. For the quasicrystals, the linear “excessive” heat capacity is observed in the range of temperatures between 400 to 600 К which means the deviation from the 3R Dulong-Petit value. The heat capacity at a temperature of 900 К is about 28.4 J/mol К which is higher than the Dulong-Petit value (~ 25 J/mol К). The “excessive” heat capacity relates to the peculiarities in the decagonal quasicrystal anisotropy. These crystals are quasiperiodic in the x and y directions, and periodic in the z direction. As a result, there is a difference in the dispersive laws in the different directions. The Debye temperature values have essential influence on the temperature dependencies of the heat capacity of the decagonal quasicrystals. Thus, the higher the Debye temperature and the larger “excessive” heat capacity, the more stable are considered the quasicrystals exposed to the temperature effects.

Role of Thermal Expansion and Redistribution of Components on the Temperature Dependence of the Lattice Misfit in γ/γ' Superalloys

2006 ◽  
Vol 980 ◽  
Author(s):  
Oleg Kontsevoi ◽  
Yuri N. Gornostyrev ◽  
Arthur J. Freeman
Keyword(s):  
Thermal Expansion ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Temperature Dependence ◽  
Temperature Region ◽  
Lattice Misfit ◽  
Slight Variation ◽  
Relative Role ◽  
The Difference

AbstractThe relative role of thermal expansion and redistribution of alloy components in the temperature dependence of the lattice misfit in γ/γ' alloys is investigated on the basis of ab initio calculations. We show that in a wide temperature region up to approximately 0.6·Tmelt, the lattice misfit is determined by the difference in thermal expansion of γ and γ' phases and shows only a slight variation. For higher temperatures the redistribution of the major alloy components between the phases becomes a leading contribution to the lattice misfit.

Temperature dependence on phase evolution in the BaTiO 3 polytypes studied using ab initio calculations

2019 ◽  
Vol 120 (1) ◽  
Author(s):  
Marisa C. Oliveira ◽  
Renan A. P. Ribeiro ◽  
Elson Longo ◽  
Maurício R. D. Bomio ◽  
Fabiana V. Motta ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Temperature Dependence ◽  
Phase Evolution
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