Fermi surfaces of diborides: MgB2andZrB2

Abstract

We provide a comparison of accurate full potential band calculations of the Fermi surfaces areas and masses of MgB2 and ZrB2 with the de Haas-van Alphen date of Yelland et al. and Tanaka et al. respectively. The discrepancies in areas in MgB2 can be removed by a shift of σ bands downward with respect to π bands by 0.24 eV. Comparison of effective masses lead to orbit averaged electron-phonon coupling constants λσ=1.3 (both orbits), λπ=0.5. The required band shifts, which we interpret as an exchange attraction for σ states beyond local density band theory, reduces the number of holes from 0.15 to 0.11 holes per cell. This makes the occurrence of superconductivity in MgB2 a somewhat closer call than previously recognized, and increases the likelihood that additional holes can lead to an increased Tc.

Electronic structure, phonon spectra and electron–phonon interaction in ScB2

“…There is also small high-energy shift of the third peak in Deligoz et al [15] in comparison with our results. B mode [35]. Such an inversion of the usual sequence of mode frequencies give one wide continuous peak formed from medium-and highenergy regions.…”

Comparative study of the electronic structure, phonon spectra, and electron-phonon interaction of ZrB2and TiB2

“…The model obtained for the FS of ZrB 2 was later confirmed by improved calculations performed using the FLAPW method. 38 Recently the Fermi surfaces of ScB 2 , ZrB 2 and HfB 2 , were studied by Pluzhnikov et al 21 using the dHvA effect. Their results for ZrB 2 are similar to previous measurements by Tanaka.…”

“…Rosner et al 38,43 provided a comparison of full potential band calculations of the Fermi surfaces areas and masses of MgB 2 and ZrB 2 with dHvA data for several symmetry points in the Brillouin zone (BZ). They found, with one possible exception, that LDA provides a good description for ZrB 2 .…”

“…32,33 First-principles calculations of the electronic structure of diborides have been widely presented. [25][26][27]30,[34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] Despite a lot of publications, there are still many open questions related to the electronic structure and physical properties of transition metal diborides. Ihara et al 27 calculated the band structure and the density of states (DOS) of ZrB 2 by using an augmented plane wave method.…”

Response of Critical Temperature of the Superconducting Transition and Energy Gaps of MgB$_2$ to the Hydrostatic Compression

“…Расчёты из первых принципов электронной структуры MgB 2 [6,36,37] показывают хорошее согласие с эôôектом де Ãааза-ван Альôена [38]. Аналогичные вычисления, дополненные расчётом ôононной структуры, показали, что в кристаллах MgB 2 давление должно уменьшать как параметр ∆ σ , так и ∆ π [30].…”