Electronic structure and superconductivity in Pd-Ag-H and Pd-Rh-H alloys

Abstract

Using the augmented-plane-wave method we have calculated the energy bands and the densities of states (DOS) of RhH, PdH, and AgH. We have also calculated the DOS for the nonstoichiometric hydrides Pd&~A SH"and Pd& yRhyHz within the virtual-crystal approximation (VCA) and the rigid-band approximation (RBA). We present evidence from coherentpotential-approximation calculations that our DOS values in the vicinity of the Fermi level are reliable. The DOS decomposed per site and angular-momentum component are used to calculate the electron-phonon interaction and the superconducting transition temperature, T" for various compositions of the above alloys. Our results are in good agreement with experiment and provide a satisfactory understanding of the variation of T, with x and v and also of the isotope effect in these systems.

Recent Developments in Condensed Matter Physics

“…Zero-point fluctuations of the TA modes thus stabilize the TO soft mode and prevent the crystal from being ferroelectric at OOK21. Migoni et al 23 equally well fitted another model based on the anisotropy in the oxygen polarizability to the same experimental data and predict that .the coefficient A of Eq. (2) should slightly decrease on increasing temperature above 50 K.…”

“…(I8), (19) and (23) lead to the interpretation of the observed correlation between T and m b,E = E + E (or E ) 4; (iii) The dependence of T on X ,S and v v m v v other material parameters given by Eq. (23) can also help to interpret the experimental data; (iv) Dependences of A on diffusion and material parameters, according to Eqs. (22) and (24), lead to a reasonable interpretation of observations; (v) Materials which display peCUliarities in the melting process also show the corresponding ones in diffusion.…”

Effects of Ba doping on the structural and electronic properties of La$_{2-x}$Ba$_x$CuO$_4$

“…The muffin-tin sphere radii, Rmt (in atomic units), were 2.15 for La, 1.72 for Cu and 1.48 for O. For the substitution of Ba for La, we used the Virtual Crystal Approximation (VCA) 18,19 . The La (Z = 57) sites are substituted for pseudo-atoms which have a fractional electronic charge (Z = 57 − x), depending on the Ba concentration x.…”

On the use of Monkhorst–Pack scheme to evaluate superconductivity and the issue of umklapp electron–phonon interactions

“…In 1972 and 1978, Ganguly and Papaconstanstopoulos investigated the reversed isotope effect in palladium hydrides theoretically. 8,9 In 2020, Semenoka and colleagues reported a rule to predict the maximum T c for metal hydrides. 10 Meanwhile, Flores-Livas and colleagues offered an up-to-date perspective on conventional superconductivity in hydrides at high pressures.…”