Electronic heat capacity lanthanum

Lanthanum exists in modified hexagonal (a) and face-centred cubic ( 8) forms, each of which contributes independently to the electronic and lattice heat capacities. Both phases display superconductivity, the transition temperatures being Ta = 4.9 K and = 6.0 K, respectively (Finnemore et al., 1965 Finnemore and Johnson, 1966). 

Measurements on LaY alloys (Ohtsuka and Satoh 1966) failed to shed light on the role of the 4f electrons in the superconductivity of lanthanum. But we can say a few more words about y. The variation of y with yttrium content shows values of 10.0 mJ/mole-K at 100% a-La and 10.5 mJ/mole-K at 100% Y. The y versus concentration curve falls from either end, but shows an irregularity in the region of Lao.sYos where the alloy has the complex a-Sm structure. Thus y for the rare earths is perhaps more closely structure dependent than was first assunted, and care must be taken when adopting a y value for separating off the electronic term in the heat capacity (see also section 1.3 above). 

In fact, the contribution of electronic conductivity can be ignored because it is quite small. The major contribution to Cp arises from the lattice (vibrational) component Cy, which varies linearly as a function of molar volume V in a series of isomorphous compounds. For the com-poimds imder study, Cy can therefore be estimated using volume-weighted interpolation (Westrum et al., 1989) and data on isomorphous diamagnetic substances as reference values. For instance, the Cy heat capacities measured for trivalent lanthanum, gadolinium, and lutetium compoimds were used as reference values. Subsequently, the Cm and Csch contributions were determined by subtracting the sum of the Cy and Cd contributions from the experimental Cp values. 

Laboratory reagents, preparation of, 8-1 to 4 Laboratory Solvents and Other Liquid Reagents, 15-13 to 22 Laguerre polynomials, A-83 to 85 Lanthanum see also Elements electrical resistivity, 12-39 to 40 electron configuration, 1-18 to 19 heat capacity, 4-135 history, occurrence, uses, 4-1 to 42 ionization energy, 10-203 to 205 isotopes and their properties, 11-56 to 253 magnetic susceptibility, 4-142 to 147 molten, density, 4-139 to 141 physical properties, 4-133 to 134 thermal properties, 12-201 to 202 vapor pressure, 6-61 to 90 vapor pressure, high temperature, 4-136 to 137... 

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