Thermal expansion of neptunium

The influence of phonon anharmonicity on thermal and elastic properties of neptunium

“…The discrepan cies can be explained by the fact that the experimental data shown in Fig. 5 was obtained not by direct density measurements but has been converted from the data [10] on the relative elongation of the sample. Fig.…”

“…Fig. 2 shows the calculated temperature depende ncies of the volumetr ic thermal expansion coefficient of neptunium in comparison with the experime ntal data [10]. Both a-and b-Np exhibit VCTE values, which are record high in comparis on with other metals, e.g.…”

“…Since according to [10] the phase transition from a to b phase occurs in the temperature range from 538 to 558 K, in all the figures we plot the data for both phases considered in this temperature range. Fig.…”

“…In the case of b-Np the electronic heat capacity coefficient is probably different , but keeping in mind that there is no any kind of experime ntal data for heat capacity of b-Np, to a first approximation one can adopt the value 14.2 mJ/K 2 for calculatin g the properties of both phases considered. As already mentioned above for neptunium there is rather limited amount of the available experimental data, but the availability of the data [10] on VCTE and mass density enabled us to make an estimation of the parameters, characterizi ng the phonon anharmonicity of a-and b-phases of Np and perform the self-consiste nt calculations of the thermal end elastic properties. The obtained values for the parameters are listed in Table 1.…”

“…At the same time there is a number of indications to that Np can be characterized by strong anharmonici ty of its lattice vibrations (the phonon anharmonicity ), e.g. the enhanced values of its volumetric thermal expansion coefficient [10] and heat capacity [7,8]. The phonon anharmonici ty of neptunium as well as its electronic subsystem can provide nonlinear in temperat ure contributions to the thermal and elastic properties (in particular , to the heat capacity).…”