Pressure induced magnetic, electronic and mechanical properties of SmX (X = Se, Te)

Abstract

The magnetic, structural, elastic and electronic properties of Sm-chalcogenides in the stable [Formula: see text] and high pressure [Formula: see text] phase have been analyzed using an ab initio pseudo-potential method with a spin-polarized GGA based on exchange-correlation energy optimization, as implemented in SIESTA code. The magnetic phase stability has been determined from the total energy calculations in non-magnetic and magnetic phases, which clearly indicate that at ambient and high pressures, these compounds are ferromagnetically stable. Also, the Sm ion is described in both five and six localized f electrons. Under compression the Sm chalcogenides undergo a first-order transformation from Sm(2+) to a stable valence state (Sm(3+)) with delocalization of the 4f electrons into the 5d states of Sm followed by a structural transition from the B1 to the B2 phase. The structural properties namely, equilibrium lattice constant, bulk modulus, its pressure derivative, transition pressure and volume collapse agree well with the experimental results. We have also computed the electronic structure at different volumes.

Effect on Charge Transfer and Charge Recombination by Insertion of a Naphthalene‐Based Bridge in Molecular Dyads Based on Borondipyrromethene (Bodipy)

“…b) A 2D device cross section27 is shown to accentuate the HYM surround and the void space. c) Finite element simulation of the PET device stack in a cylindrical geometry performed using the ANSYS software and the materials properties of Refs 18, 19…”

“…Together, low PE stress and strain along with appropriate gate–common fields act to prevent degradation of the PE during operation. In Figure 1c a static linear piezo‐elastic16–19 based finite element model computation of the stress in the PET structure in the ON state shows the basic principles (high stress in the PR is generated through the application of low gate–common voltage while maintaining low stress in the PE); the HYM is included explicitly in the computation.…”

High pressure phase-transition, elastic and thermal properties of uranium chalcogenides: A model study

“…The negative Cauchy's discrepancy is a consequence of the hybridization of the unstable f band, which maybe responsible for the decrease in U-U distance thereby to small value of elastic constant C 12 . The elastic anisotropic factor (A) used in the interpretation of the seismological and shear-wave velocities anisotropy as reported in Table 3 shows that these compounds are anisotropic (if "A" approaches unity the crystal becomes isotropic) but it is comparatively large as compared to others materials of rare-earth family [36]. and Srivastava et al [18] show that C 12 − C 44 = 0, while their results show different values of C 12 and C 44 and hence their results are not reliable.…”

Pressure effect on magnetic susceptibility of SmS in the “black” phase

“…At a critical pressure P c ∼ 6.5 kbar and room temperature SmS undergoes the first order isostructural phase transition to a mixed-valent metal state accompanied by a significant volume collapse of about 13 % and a color change from black to golden-yellow [1][2][3][4]. According to theoretical calculations of the volume dependent electronic structure of SmS, SmSe an SmTe (see, for example, [5][6][7][8]) this transition, being typical for the whole series [1,4,9,10], is related to the closure under pressure of the semiconducting gap ∆, whose values at zero pressure are listed in table I. [11], pressure derivative d∆/dP [2], lattice parameter a at room temperature [12], experimental values of the magnetic susceptibility χ(0) at T → 0 K with the subtracted impurity effects [12,13].…”