Effect of ordering on the specific heat of Cu3Au below 3 °K

1968 ◽  
Vol 46 (8) ◽  
pp. 923-927 ◽  
Author(s):  
Douglas L. Martin
Keyword(s):  
Elastic Constant ◽  
Specific Heat ◽  
Electric Quadrupole ◽  
Quadrupole Moments ◽  
Electronic Specific Heat ◽  
Electric Field Gradients ◽  
Specific Heats ◽  
Disordered Lattice ◽  
Field Gradients ◽  
Lattice Specific Heat

Ordering reduces the nuclear, electronic, and lattice specific heats. The change in nuclear specific heat supports the hypothesis that this term in the specific heat arises from the interaction of nuclear electric quadrupole moments with electric field gradients in the disordered lattice. The small (3.5%) change in the electronic specific heat suggests little change in the Fermi surface on ordering. The change in the lattice specific heat is greater than expected from elastic constant measurements on ordered and disordered Cu3Au.

Specific heat below 3 °K of a gold–zinc and a gold–indium alloy

1969 ◽  
Vol 47 (10) ◽  
pp. 1077-1081 ◽  
Author(s):  
Douglas L. Martin
Keyword(s):  
Specific Heat ◽  
Face Centered Cubic ◽  
Electronic Specific Heat ◽  
Confidence Limits ◽  
Electric Field Gradients ◽  
Field Gradients ◽  
Atomic Silver ◽  
Face Centered ◽  
Specific Heat Coefficient ◽  
Limiting Value

Face-centered-cubic alloys of gold with 10 atomic % zinc (divalent) and 10 atomic % indium (trivalent), respectively, were measured in the range 0.4 to 3.0 °K. The coefficients of the nuclear specific-heat term were 1.80 ± 0.07 μcal °K/g atom for AuZn and 1.29 ± 0.06 μcal °K/g atom for AuIn (95% confidence limits). For a gold–10 atomic % silver (monovalent) alloy (Martin 1968) the nuclear term was 0.44 μcal °K/g atom. These results show that electric field gradients in alloys are not simply proportional to the valence difference of the components, a conclusion which may be drawn from NMR results. For the AuZn alloy the electronic specific-heat coefficient (γ) is 153.4 ± 0.7 μcal/°K2 g atom and the limiting value of the Debye temperature (θ0c) is 177.0 ± 0.5 °K. For the AuIn alloy γ is 185.9 ± 0.7 μcal/°K2 g atom and θ0c is 159.1 ± 0.3 °K.

scholarly journals Thermodynamic Properties of La1-xSmxCoO3

2014 ◽  
Vol 2014 ◽  
pp. 1-5
Author(s):  
Rasna Thakur ◽  
N. K. Gaur
Keyword(s):  
Experimental Data ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Bulk Modulus ◽  
Specific Heat ◽  
Specific Heats ◽  
Lattice Specific Heat ◽  
Lattice Distortions ◽  
First Time ◽  
Rigid Ion Model

We have investigated the bulk modulus and thermal properties of La1-xSmxCoO3 (0≤x≤0.2) at temperatures 1 K≤T≤300 K probably for the first time by incorporating the effect of lattice distortions using the modified rigid ion model (MRIM). The calculated specific heat, thermal expansion, bulk modulus, and other thermal properties reproduce well with the available experimental data, implying that MRIM represents properly the nature of the pure and doped cobaltate. The specific heats are found to increase with temperature and decrease with concentration (x) for the present. The increase in Debye temperature (θD) indicates an anomalous softening of the lattice specific heat because increase in T3-term in the specific heat occurs with the decrease of concentration (x).

The nuclear quadrupole moment of 69Ga and 115In

2009 ◽  
Vol 87 (7) ◽  
pp. 802-805 ◽  
Author(s):  
Hana Yakobi ◽  
Ephraim Eliav ◽  
Uzi Kaldor
Keyword(s):  
Electric Field ◽  
Fock Space ◽  
Coupling Constants ◽  
Basis Sets ◽  
Coupled Cluster ◽  
Quadrupole Moments ◽  
Electric Field Gradients ◽  
Field Gradients ◽  
Nuclear Quadrupole ◽  
Nuclear Quadrupole Moments

Electric field gradients at the nuclei of gallim and indium are determined by finite field calculations of the atomic energies as functions of the nuclear quadrupole moments. The four-component Dirac–Coulomb–Gaunt Hamiltonian serves as framework, and all electrons are correlated by Fock-space coupled cluster with single and double excitations or by single reference coupled cluster with approximate triples. Large, converged basis sets (e.g., 28s24p20d13f5g4h for In) and virtual spaces are used. Together with experimental nuclear quadrupole coupling constants, known with high precision, the calculated electric field gradients yield the nuclear quadrupole moments. For 69Ga, we get Q = 174(3) mb, in agreement with the earlier 171(2) mb obtained from molecular calculations. The 115In moment is Q = 772(5) mb, considerably lower than the previously accepted 810 mb, and in good agreement with the recent molecular value of 770(8) mb.

Electric Field Gradients Around Point Defects in Metals

1996 ◽  
Vol 51 (5-6) ◽  
pp. 489-505
Author(s):  
Alfred Seeger ◽  
Jörg Ehmann ◽  
Manfred Fähnle
Keyword(s):  
Electric Field ◽  
Ab Initio ◽  
Density Functional ◽  
Local Density ◽  
Energy Levels ◽  
Full Potential ◽  
Good Resolution ◽  
Quadrupole Moments ◽  
Electric Field Gradients ◽  
Field Gradients

The splittings of nuclear energy levels caused by the electric field gradients acting on the quadrupole moments of nuclei in the neighbourhood of atomic defects in cubic metals may serve as ‘‘fingerprints’’ providing us with a unique characterization of these defects. In favourable cases the NQDOR technique (n̲uclear q̲uadrupole d̲ouble r̲esonance) permits sensitive measurements of these splittings with good resolution. The present paper outlines the status of the ab-initio calculation of electric field gradients with emphasis on the theoretical basis (density functional theory with local density approximation) and on the techniques required for handling the specific problems associated with defects. Recent work by the supercell approach on atomic defects in Al and Cu, making use either of the full-potential linearized augmented-plane-wave method or of the ab-initio pseudopotential method, are reported and compared with experiments. The excellent agreement between experiment and theory for the field gradients acting on the nearest-neighbour nuclei of monovacancies in Al demonstrates the reliability and the potential of the theory.

The nuclear electric quadrupole moment of copper

2014 ◽  
Vol 16 (23) ◽  
pp. 11590-11596 ◽  
Author(s):  
Régis Tadeu Santiago ◽  
Tiago Quevedo Teodoro ◽  
Roberto Luiz Andrade Haiduke
Keyword(s):  
Regression Analysis ◽  
Linear Regression ◽  
Quadrupole Moment ◽  
Linear Regression Analysis ◽  
Electric Quadrupole ◽  
Electric Quadrupole Moment ◽  
Electric Field Gradients ◽  
Field Gradients ◽  
Accepted Standard ◽  
Standard Value

A new nuclear electric quadrupole moment was determined for the63Cu nucleus by means of a linear regression analysis of experimental nuclear electric quadrupole constants against electric field gradients obtained from relativistic calculations at several levels, which suggests a revision of the currently accepted standard value for this property.

Low temperature specific heats of zinc alloyed with silver

1975 ◽  
Vol 343 (1634) ◽  
pp. 363-374 ◽  
Keyword(s):  
Low Temperature ◽  
Fermi Level ◽  
Specific Heat ◽  
Debye Temperature ◽  
Density Of States ◽  
Electronic Specific Heat ◽  
Pure Zinc ◽  
Specific Heats ◽  
Complete Breakdown ◽  
Specific Heat Coefficient

Measurements of the electronic specific heat coefficient and of the limiting Debye temperature are reported for pure zinc and for two n-phase alloys containing 2 at. % and 4 at. % silver in zinc, respectively. After a correction for electron-phonon enhancement the electronic specific heat coefficient for pure zinc differs by only a small percentage from the calculated value reported in the literature on the basis of a band calculation. The results for the alloys show a decreasing trend of the density of states at the Fermi level when silver is added to zinc. This is contrary to a prediction based on a rigid band approach. Hence, the results indicate a complete breakdown of the rigid band condition on alloying. The reasons for this are most likely associated with the influence of the d band electrons or with charge distribution effects between solute and solvent atoms.

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