Fermi surface properties of AB₃(A = Y, La; B = Pb, In, Tl) intermetallic compounds under pressure

Abstract

The electronic structures, densities of states, Fermi surfaces and elastic properties of AB3 (A =La, Y; B =Pb, In, Tl) compounds are studied under pressure using the full-potential linear augmented plane wave (FP-LAPW) method within the local density approximation for the exchange-correlation functional and including spin-orbit coupling. Fermi surface topology changes are found for all the isostructural AB3 compounds under compression (at V/V0 = 0.90 for LaPb3 (pressure = 8 GPa), at V/V0 = 0.98 for AIn3 (pressure = 1.5 GPa), at V/V0 = 0.80 for ATl3 (pressure in excess of 18 GPa)) apart from YPb3, although its electronic structure at zero pressure is very similar to that of LaPb3. For LaPb3 a softening of the C44 elastic constant under pressure (equivalent to 8 GPa) may be related to the appearance of a new hole pocket around the X point. From the calculated elastic properties and other mechanical properties, all the compounds investigated are found to be ductile in nature with elastic anisotropy. The states at the Fermi level (EF) are dominated by B p states with significant contributions from the A d states. For the La compounds, small hybridizations of the La f states also occur around EF.

Role of spin-orbit coupling in the physical properties of LaX3 ( X=In , P, Bi) superconductors

“…In particular, the calculated lattice parameters for these intermetallic compounds with and without SOC are found to differ by less than 2% from their experimental values [30,31,43]. The presented values of bulk modulus for LaIn 3 and LaPb 3 materials are in gratifying agreement with previous LDA results [41], with a maximum difference of 5.0% for LaPb 3 . However, our LDA results for the bulk modulus of LaIn 3 and LaPb 3 considerably differ from their corresponding GGA values [42], with a maximum difference of 28% for LaIn 3 .…”

“…For example, the values of a, B, and B for LaPb 3 (LaBi 3 ) change by 0.08% (0.14%), 2.64% (3.64%), and 5.50% (8.33%), respectively, with inclusion of the SOC. The calculated values of the three independent elastic constants for LaX 3 are presented in Table I along those reported in previous theoretical calculations [41,42]. However, no experimental results are available for comparison.…”

“…The calculated values for the equilibrium lattice parameter (a), the bulk modulus (B), and its pressure derivative (B ) with and without SOC are presented in Table I along with existing experimental [30,31,43] and theoretical [41,42] results. The calculated lattice constants for LaX 3 compare very well with previous experimental [30,31,43] and theoretical values [41,42]. In particular, the calculated lattice parameters for these intermetallic compounds with and without SOC are found to differ by less than 2% from their experimental values [30,31,43].…”

“…However, their calculations have been made within the generalized gradient approximation (GGA) rather than the LDA. A comparison of these two FP-LAPW [41,42] works shows that the values of the calculated second-order elastic constants for LaIn 3 differ from each other within around 30%. This difference can be related to the different exchange-correlation approximations used in these FP-LAPW works [41,42].…”

“…This theoretical work indicates that the interaction between La d and In p forms the main bonding states in this superconductor, thus suggesting that this material acts like a transition metal compound. After this theoretical work, the electronic and elastic properties of LaX 3 (X = Pb, In, and Tl) have been presented under pressure using the FP-LAPW method within the local density approximation (LDA) [41]. This theoretical work proposes that the bands near the Fermi level for these superconductors consist mostly of X p orbitals with significant contributions from La d orbitals.…”