Effect of phonon anharmonicity on the thermophysical and elastic properties of platinum

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

“…Both a-and b-Np exhibit VCTE values, which are record high in comparis on with other metals, e.g. transition metals palladium and platinum [12], and which are comparable to alpha-plutoni um [14]. As can be seen from Fig.…”

“…As in the case of VCTE neptunium demonst rates the values of Gruneisen parameter that are much higher as compared to transition metals. Thus, for palladium and platinum in the entire range of their existence C does not exceed 3.1 [12]. Comparing to plutonium [5] we can point that neptunium possess the values of the Gruneise n parameter, which are typical for d-Pu (C = 3.8 at T = 480 K) but higher than in the case of b-Pu (C = 2.3 at T = 450 K) and c-Pu (C = 1.9 at T = 550 K).…”

“…It should be noted that the Poisson coefficient r, which strongly affects the Debye temperature and (as a consequence) all thermal and elastic properties, can be determined from either data on elastic modules [5] or on the mean-sq uare displacemen t (MSD) of atoms from the equilibrium positions [12]. However, in the case of Np experimental data neither on elastic modules nor on MSD is available.…”

“…In the presence of anharmonicity the sum over all modes will no longer equal 3NkT and this can be taken into account via temperature -dependent characterist ic Debye temperature. Exactly such an approach is implemented in the self-consistent thermodyna mic model [11][12][13] …”

“…In the papers [11][12][13] a self-consi stent thermodynam ic model has been developed, which on the basis of generalization of the Debye model, describes the effect of phonon anharmonicity on the thermal and elastic properties of metals. This model enabled to describe the unusual temperature dependenci es of thermal properties of plutoniu m [13] and correctly determine the electronic contributi ons that in case of Pu are also affected by the spin anharmonicity [3,13].…”