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Theoretical investigation on TbTe for its structural, electronic, magnetic, and thermodynamic stuffs has been carried within density functional theory (DFT) as implemented in WIEN2K code. TbTe was found stable in ferromagnetic phase. The calculated ground-state parameters were found in a good agreement with the experimental data. The compound was found to have a structural stability in cubic B1 (NaCl-type structure) phase, but under the application of high pressure (at 27 GPa), it undergone to B2 (CsCl-type structure) phase of pressure. The second-order elastic constants and mechanical properties like Young’s modulus, Shear modulus, Poisson ratio, Cauchy pressure (C12-C44), and Pugh’s ratio (B/G) were calculated. The present calculations confirmed the ductile nature of TbTe. Further, the thermodynamic investigations have been carried using quasi-harmonic Debye approximation. We have calculated the pressure and temperature dependence of Debye temperature (휃D), bulk modulus (B), thermal expansion (α), heat capacities (CV), and entropy (S) in the temperature range of 0 to 1000 K and pressure range of 0 to 25 GPa. [ABSTRACT FROM AUTHOR]

Abstract: The structural and mechanical properties of LnO (Ln=Sm, Eu, Yb) compounds have been investigated using a modified interionic potential theory, which includes the effect of Coulomb screening. We predicted a structural phase transition from NaCl (B1)- to CsCl (B2)-type structure and elastic properties in LnO compounds at very high pressure. The anomalous properties of these compounds have been correlated in terms of the hybridisation of f-electrons of the rare earth ion with conduction band and strong mixing of f-states of lanthanides with the p-orbital of neighbouring chalcogen ion. For EuO, the calculated transition pressure, bulk modulus and lattice parameter are close to the experimental data. The nature of bonds between the ions is predicted by simulating the ion–ion (Ln–Ln and Ln–O) distances at high pressure. The second order elastic constants along with shear modulus and Young''s modulus, elastic anisotropy and Poisson''s ratio are also presented for these oxides. [Copyright &y& Elsevier]

The results of first principles calculations of the electronic band structures, density of states, band gap, equilibrium lattice constants, cohesive energies, bulk moduli and magnetic moments are presented for the EuN with rock salt as ambient structure and cesium chloride as high-pressure structure. The tight-binding linear muffin tin orbital method within the local-density approximation is used. Both spin-polarized and non-spin polarized calculations are performed. The magnetic and structural stabilities are determined from the total energy calculations for both nonmagnetic (NM) and ferro-magnetic (FM) states. From the present study EuN illustrates half-metallic. The FM phase is more stable than NM phase. We further predict EuN undergoes a transition from NaCl-type (B1) to CsCl-type structure (B2) at 14.6 GPa, which could not be compared owing to the need of experimental and theoretical results. Futhermore, the bulk moduli, first-order pressure derivatives and magnetic moments are also estimated in B1 and B2 phases. The magnetic moment is estimated to be nearly 6 μB, which is in good agreement with the others reported value. A small decrease in magnetic moment is observed under pressure. [ABSTRACT FROM AUTHOR]

Abstract: We present the results of theoretical calculations on the structural, magnetic and electronic properties of Er-monopnictides using self-consistent first principles tight-binding linear-muffin-tin-orbital (TB-LMTO) method within the atomic-sphere approximation (ASA). Both spin-polarized and non-spin-polarized calculations are performed to check the magnetic stability of these compounds. We find that ErN, ErP and ErAs are metallic in ferromagnetic (FM) phase in both the spin channels and stable in NaCl-type (B1) structure at ambient pressure. We predict NaCl-type (B1) to CsCl-type (B2) structural phase transition in ErN, ErP and ErAs at pressures of 146.1, 60.2 and 53.2GPa, respectively and remain metallic ferromagnetic at high pressure. We calculate equilibrium lattice constants (a), bulk modulus (B), magnetic moments (μB) and electronic properties of these compounds in B1 and B2 phases and compare with available experimental and theoretical results. [Copyright &y& Elsevier]

The structural and elastic properties of praseodymium monochalcogenides (PrX: X = S, Se, Te) and monopnictides (PrY: Y = P, As, Sb, Bi) with NaCl-type structure have been investigated by using an interionic potential theory with necessary modification to include the effect of Coulomb screening due to the delocalized f-electrons of rare earth ion. The calculations are done at ambient as well as at high pressure. The structure of the high pressure phase of PrX compounds is CsCl-type while all the PrY compounds have been found to undergo from their initial NaCl-type structure to high pressure body centered tetragonal (BCT) structure, which can be seen as the distorted CsCl-type with c/a ratio ≈ 0.82-0.87. The calculated transition pressures are in good agreement with the experimental results. The elastic properties like second-order elastic constants for PrX, Y compounds are calculated for the first time. The nature of the bonding is also predicted by calculating the distance between the ions with the increasing pressure. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated, the cohesive energies, equilibrium lattice constants, pressure–volume relationship, phase transition pressure (P T), elastic constants and variation of elastic constants with pressure for yttrium pnictides (YX; X=N, P, As and Sb), using an interionic potential theory with modified ionic charge which, includes Coulomb screening effect due to d-electrons. These compounds undergo structural phase transition from NaCl (B1) to CsCl (B2) structure at high pressure (ranges 20–130GPa). We have also calculated bulk (BT ), Young (E), and shear moduli (G), Poisson ratio (υ) and anisotropic ratio (A) in NaCl (B1)-type structure for yttrium pnictides and compared them with other experimental and theoretical results which show a good agreement. [Copyright &y& Elsevier]

Abstract: The tight-binding linear muffin tin orbital (TB-LMTO) method within the local density approximation is used to calculate structural, electronic and magnetic properties of GdN under pressure. Both nonmagnetic (NM) and magnetic calculations are performed. The structural and magnetic stabilities are determined from the total energy calculations. The magnetic to ferromagnetic (FM) transition is not calculated. Magnetically, GdN is stable in the FM state, while its ambient structure is found to be stable in the NaCl-type (B1) structure. We predict NaCl-type to CsCl-type structure phase transition in GdN at a pressure of 30.4GPa. In a complete spin of FM GdN the electronic band picture of one spin shows metallic, while the other spin shows its semiconducting behavior, resulting in half-metallic behavior at both ambient and high pressures. We have, therefore, calculated electronic band structures, equilibrium lattice constants, cohesive energies, bulk moduli and magnetic moments for GdN in the B1 and B2 phases. The magnetic moment, equilibrium lattice parameter and bulk modulus is calculated to be 6.99 μ B, 4.935Å and 192.13GPa, respectively, which are in good agreement with the experimental results. [Copyright &y& Elsevier]

Abstract: The electronic, structural and magnetic properties of half-metallic promethium nitride (PmN) have been studied using first-principles tight-binding linear muffin-tin orbital (TB-LMTO) method within the local-density approximation (LDA). We calculate the total energy, lattice parameter, bulk modulus, magnetic moment, density of states and energy band structures of half-metallic PmN at ambient as well as at high pressure. Both spin-polarised and non-spin-polarised electronic calculations are performed to check the magnetic stability of PmN. It is found that PmN is ferromagnetically stable. From the total energy calculations it is also found that PmN is stable in the NaCl-type structure under ambient conditions. The structural stability of PmN changes under the application of pressure. We predict a structural phase transformation from NaCl- to CsCl-type structure at the pressure of 3.4GPa. The high-pressure phase of PmN remains half-metallic and ferromagnetic. The calculated equilibrium lattice parameter and bulk modulus are in good agreement with the experimental and theoretical work. [Copyright &y& Elsevier]

Abstract: A study on structural and electronic properties of non-magnetic cubic B2-type AlRE (RE=Sc, Y, La, Ce, Pr and Lu) intermetallics has been done theoretically. The self-consistent tight binding linear muffin tin orbital method is used to describe the electronic properties of these intermetallics at ambient and at high pressure. These compounds show metallic behavior under ambient conditions. The variation of density of states under compression indicates some possibility of structural phase transformation in AlLa, AlCe and AlPr. Thermal properties like Debye temperature and Grüneisen constant are calculated at T=0K and at ambient pressure within the Debye–Grüneisen model and compared with the others’ theoretical results. Our results are in good agreement. We have also performed a pressure-induced variation of Debye temperature and have found a decrease in Debye temperature around 40kbar in AlRE (RE=La, Ce, Pr) intermetallics. [Copyright &y& Elsevier]

Pressure-induced structural phase transitions at high-pressure in monosulfides of thorium, uranium, neptunium and plutonium (AnS) have been studied theoretically by an inter-ionic potential theory with modified ionic charge introduced to include the Coulomb screening effect due to localized 'f' electrons. These AnS compounds undergo a phase transition from sodium chloride (NaCl) to cesium chloride (CsCl) structure at a very high-pressure. The present theoretical investigation carried out up to 120 GPa reveals that these compounds undergo NaCl-CsCl phase transitions at 100, 81, 75 and 105 GPa for ThS, US, NpS and PuS, respectively. The first-order pressure derivatives calculated from the present theory agree well with observed data. [ABSTRACT FROM AUTHOR]

Abstract: Pressure-induced structural phase transition of gadolinium monopnictides GdX (X=As and Sb) has been studied theoretically using an inter-ionic potential theory. This method has been found quite satisfactory in case of the pnictides of rare-earth and describes the crystal properties in the framework of rigid-ion model. We have modified the ionic charge so that it may include the Coulomb-screening effect by the delocalization of f electron of the rare-earth ion. The anomalous structural properties of these compounds with many f electrons have been interpreted in terms of the hybridization of f electrons with the conduction band and strong mixing of f states of Gd ion with the p orbital of neighbouring pnictogen ion. Both the compounds are found to undergo from their initial NaCl (B 1) structure to body centered tetragonal (BCT) structure at high pressure and agree well with the experimental results. The BCT structure is viewed as distorted CsCl structure and is highly anisotropic with c/a=0.82–0.85. The nature of bonds between the ions is predicted by simulating the ion–ion (Gd–Gd and Gd–X) distance at high pressure. Elastic properties of these compounds have also been studied with their second-order elastic constants. [Copyright &y& Elsevier]