High Temperature NMR Study of 51V and 195Pt in the V3Pt Compound

1984 ◽  
Vol 39 (2) ◽  
pp. 145-147
Author(s):  
R. Rünger ◽  
D. Ploumbidis
Keyword(s):  
High Temperature ◽  
Temperature Dependence ◽  
Knight Shift ◽  
Core Polarization ◽  
Temperature Coefficients ◽  
Polarization Contribution ◽  
The Core ◽  
Nmr Study

Measurements of both the 51V and 195Pt Knight shift in the V3Pt compound are reported for temperatures ranging from 300 K to about 1300 K. The temperature coefficients of the Knight shift and the NMR linewidth have been determined. An interpretation of the observations is given in the frame of a model which is based on the temperature dependence of the core polarization contribution to the total Knight shift.

Knight Shift in the V3Ga Compound at High Temperatures

1984 ◽  
Vol 39 (2) ◽  
pp. 201-202
Author(s):  
R. Rünger ◽  
D. Ploumbidis
Keyword(s):  
Temperature Dependence ◽  
High Temperatures ◽  
Knight Shift ◽  
Entire Range ◽  
Temperature Dependent ◽  
Core Polarization ◽  
Polarization Contribution ◽  
The Core ◽  
Model Based ◽  
Dependent Term

The temperature dependence of the Knight shift of both 51V and 71Ga in the V3Ga compound has been measured over the entire range from 300 K to 1300 K. The results are discussed using a model based on the assumption that the core polarization contribution to the total Knight shift is the temperature dependent term.

Calculation of the Knight Shift in Palladium

1979 ◽  
Vol 34 (4) ◽  
pp. 523-524 ◽  
Author(s):  
R. Krieger ◽  
J. Voitländer
Keyword(s):  
Fermi Surface ◽  
Knight Shift ◽  
Enhancement Factor ◽  
Negative Contribution ◽  
Core Polarization ◽  
Conduction Electrons ◽  
The Core ◽  
Core Electrons ◽  
Palladium Metal ◽  
Good Agreement

The direct and core-polarization contributions to the Knight shift in palladium metal have been calculated taking an enhancement factor of 10 for d- and 1.28 for s-electrons. We found a large negative contribution of - 3.88% for the core electrons and a comparatively small direct contribution of 0.18% for s-electrons on the Fermi surface. Together with an estimated contribution of 0.36% for conduction electrons in s-orbitals, but not on the Fermi surface, the calculated total amount of - 3.34% is in good agreement with the experimental value of - 4% obtained by the Jaccarino plot for palladium at 0 K

Core-Polarization Contribution to the Knight Shift in Beryllium Metal

1966 ◽  
Vol 141 (2) ◽  
pp. 603-615 ◽  
Author(s):  
Wei-Mei Shyu ◽  
G. D. Gaspari ◽  
T. P. Das
Keyword(s):  
Knight Shift ◽  
Core Polarization ◽  
Polarization Contribution ◽  
Beryllium Metal

Higher Order Core Polarization Contributions to the Effective Interaction in 42Ca – 42Sc

1973 ◽  
Vol 51 (21) ◽  
pp. 2275-2282 ◽  
Author(s):  
A. M. Jopko ◽  
Donald W. L. Sprung
Keyword(s):  
Numerical Calculation ◽  
Effective Interaction ◽  
Closed Shell ◽  
Higher Order ◽  
Core Polarization ◽  
Polarization Contribution ◽  
The Core ◽  
The One

A numerical calculation of the core polarization of the effective interaction between nucléons outside the 40Ca closed shell has been carried out, taking account of several higher order processes suggested by Kirson. These are a systematic inclusion of particle–hole scattering, self-screening of phonons, and modification of the one-particle to two-particle, one-hole vertex. These processes have the same effect as in the earlier calculation for 16O; namely, the final result is a very small net core polarization contribution to the effective interaction, which cannot explain the low-lying spectra.

Exsolution and inversion in pigeonite from the Whin Sill, Northern England

1978 ◽  
Vol 36 (1) ◽  
pp. 474-475
Author(s):  
P.P.K. Smith
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Homogeneous Nucleation ◽  
Silicate Mineral ◽  
Antiphase Boundaries ◽  
Two Phase ◽  
Primitive Form ◽  
The Core ◽  
Nucleation Mechanisms ◽  
And Inversion

Grains of pigeonite, a calcium-poor silicate mineral of the pyroxene group, from the Whin Sill dolerite have been ion-thinned and examined by TEM. The pigeonite is strongly zoned chemically from the composition Wo8En64FS28 in the core to Wo13En34FS53 at the rim. Two phase transformations have occurred during the cooling of this pigeonite:- exsolution of augite, a more calcic pyroxene, and inversion of the pigeonite from the high- temperature C face-centred form to the low-temperature primitive form, with the formation of antiphase boundaries (APB's). Different sequences of these exsolution and inversion reactions, together with different nucleation mechanisms of the augite, have created three distinct microstructures depending on the position in the grain.In the core of the grains small platelets of augite about 0.02μm thick have farmed parallel to the (001) plane (Fig. 1). These are thought to have exsolved by homogeneous nucleation. Subsequently the inversion of the pigeonite has led to the creation of APB's.

ABOUT HEAT CAPACITY OF TITANIUM CARBIDE TiCx

2019 ◽  
pp. 56-66
Author(s):  
I. Khidirov ◽  
V. V. Getmanskiy ◽  
A. S. Parpiev ◽  
Sh. A. Makhmudov
Keyword(s):  
Heat Capacity ◽  
High Temperature ◽  
Titanium Carbide ◽  
Temperature Dependence ◽  
Carbon Concentration ◽  
Room Temperature ◽  
Thermodynamic Characteristics ◽  
Liquid Nitrogen Temperature ◽  
Analysis Data ◽  
Thermal Excitation

This work relates to the field of thermophysical parameters of refractory interstitial alloys. The isochoric heat capacity of cubic titanium carbide TiCx has been calculated within the Debye approximation in the carbon concentration  range x = 0.70–0.97 at room temperature (300 K) and at liquid nitrogen temperature (80 K) through the Debye temperature established on the basis of neutron diffraction analysis data. It has been found out that at room temperature with decrease of carbon concentration the heat capacity significantly increases from 29.40 J/mol·K to 34.20 J/mol·K, and at T = 80 K – from 3.08 J/mol·K to 8.20 J/mol·K. The work analyzes the literature data and gives the results of the evaluation of the high-temperature dependence of the heat capacity СV of the cubic titanium carbide TiC0.97 based on the data of neutron structural analysis. It has been proposed to amend in the Neumann–Kopp formula to describe the high-temperature dependence of the titanium carbide heat capacity. After the amendment, the Neumann–Kopp formula describes the results of well-known experiments on the high-temperature dependence of the heat capacity of the titanium carbide TiCx. The proposed formula takes into account the degree of thermal excitation (a quantized number) that increases in steps with increasing temperature.The results allow us to predict the thermodynamic characteristics of titanium carbide in the temperature range of 300–3000 K and can be useful for materials scientists.

The Microscopic Structure Of Shallow Donors In Silicon Carbide

1996 ◽  
Vol 442 ◽  
Author(s):  
J.-M. Spaeth ◽  
S. Greulich-Weber ◽  
M. März ◽  
E. N. Kalabukhova ◽  
S. N. Lukin
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Double Resonance ◽  
Epr Spectra ◽  
Electron Nuclear Double Resonance ◽  
Paramagnetic Resonance ◽  
Vacancy Pair ◽  
Temperature Spectra ◽  
Electron Paramagnetic

AbstractThe electronic structure of nitrogen donors in 6H-, 4H- and 3C-SiC is investigated by measuring the nitrogen hyperfine (hf) interactions with electron nuclear double resonance (ENDOR) and the temperature dependence of the hf split electron paramagnetic resonance (EPR) spectra. Superhyperfine (shf) interactions with many shells of 13C and 29Si were measured in 6H-SiC. The hf and shf interactions are discussed in the framework of effective mass theory. The temperature dependence is explained with the thermal occupation of the lowest valley-orbit split A1 and E states. It is proposed that the EPR spectra of P donors observed previously in neutron transmuted 6H-SiC at low temperature (<10K) and high temperature (>60K) are all due to substitutional P donors on the two quasi-cubic and hexagonal Si sites, whereby at low temperature the E state is occupied and at high temperature the A1 state. The low temperature spectra are thus thought not to be due to P-vacancy pair defects as proposed previously.

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