Development of Interatomic Potentials for FCC Metals Based on Lattice Inversion Method

Interatomic potential plays an important role in molecular dynamics simulation, which determines both the efficiency and accuracy of the simulations. Lattice inversion is a method which can be used to develop interatomic potential from first principle results directly. In present work, a robust potential model based on lattice inversion is proposed. Then the potential model is applied to develop interatomic potentials for eight common FCC metals. The cohesive energy curves calculated using first principle calculations can be well reproduced, which verifies the reliability of the developed potential. Additional physical properties, including equilibrium lattice constant and cohesive energy, elastic constants, are predicted and found reasonable agreement with corresponding first principle results.

Strain Control of the Tunable Physical Nature of a Newly Designed Quaternary Spintronic Heusler Compound ScFeRhP

Recently, an increasing number of rare-earth-based equiatomic quaternary compounds have been reported as promising novel spintronic materials. The rare-earth-based equiatomic quaternary compounds can be magnetic semiconductors (MSs), spin-gapless semiconductors (SGSs), and half-metals (HMs). Using first-principle calculations, we investigated the crystal structure, density of states, band structure, and magnetic properties of a new rare-earth-based equiatomic quaternary Heusler (EQH) compound, ScFeRhP. The results demonstrated that ScFeRhP is a HM at its equilibrium lattice constant, with a total magnetic moment per unit cell of 1 μB. Furthermore, upon introduction of a uniform strain, the physical state of this compound changes with the following transitions: non-magnetic-semiconductor-(NMS) → MS → SGS → HM → metal. We believe that these results will inspire further studies on other rare-earth-based EQH compounds for spintronic applications.

Study of Structural and Electronic Properties of Fluoride Perovskite KCaF3 using FP-LAPW Method

To study the structural and electronic properties of cubical perovskite KCaF3, the first principles calculation within the full potential linearized augmented plane wave (FP-LAPW) method is applied. The exchange correlation effects are included through the GGA exchange potential. The calculated structural properties such as equilibrium lattice constant, the bulk modulus and its pressure derivative are in agreement with the published results of other authors. From our study we have found that the band gap of KCaF3 is 6.4 eV which is the indication of insulating behavior.The Himalayan Physics Vol. 6 & 7, April 2017 (100-103)

Site preference and electronic structure of Mn2RhZ (Z = Al, Ga, In, Si, Ge, Sn, Sb): a theoretical study

The electronic structure and magnetism of Mn2RhZ (Z = Al, Ga, In, Si, Ge, Sn, Sb) Heusler alloys have been studied by using first-principles calculations. Three half-metallic ferromagnets, namely, Mn2RhAl, Mn2RhGe and Mn2RhSb have been considered. The calculated equilibrium lattice constant increases with increasing atomic number of Z atoms lying in same column of periodic table. The calculated total magnetic moments Mtot are 2 µB/f.u. for Mn2RhAl and Mn2RhGa, 3 µB/f.u. for Mn2RhSi, Mn2RhGe and Mn2RhSn, and 4 µB/f.u. for Mn2RhSb, which agrees with the Slater-Pauling curve quite well. In all these compounds, except for Mn2RhSb, the moments of Mn (A) and Mn (B) are antiparallel to each other. The total magnetic moments of the three considered half-metals assume integral values in a wide range of equilibrium lattice parameters.

Electronic structure and possible martensitic transformation in Ni2FeIn alloy

The electronic structure and magnetic properties of Heusler alloys (Ni2FeIn) have been studied by first principle calculations. The possible tetragonal martensitic transformation has been predicted and the structure optimization was made on cubic austenitic Ni2FeIn in Cu2MnAl type. The equilibrium lattice constant of austenitic Ni2FeIn is 6.03 Å. In tetragonal phase, the global energy minimum occurs at c/a = 1.29. The corresponding equilibrium lattice constants for martensite Ni2FeIn are a = b = 5.5393 Å and c = 7.1457 Å, respectively. In the austenitic phase, E F is located at the peak in the minority DOS for c/a = 0.96 to 1.20, but in the martensitic phase, E F moves to the bottom of the valley in the minority DOS, reducing the value of N(E F) effectively. Both austenitic and martensitic phases are ferromagnetic and the Ni and Fe partial moments contribute mainly to the total moments. Therefore, the martensitic transformation behavior in Ni2FeIn is predicted.

ON THE POSSIBILITY OF SMALL Mn CLUSTERS HAVING CUBIC SYMMETRY AND THEIR MAGNETIC MOMENTS

Possibility of cubic structures in small manganese ( Mn ) clusters has been studied using the linear combination of Gaussian orbitals (LCGO) method. Local spin density approximation is adopted for the exchange correlation potential. Both high-spin and low-spin states are found for Mn 13 and Mn 19 clusters with the face-centered cubic symmetry; however, no equilibrium lattice constant could be found. For Mn 9 and Mn 15 clusters with the body-centered cubic symmetry, only high-spin states are found. No equilibrium lattice constant could be found for bcc Mn 9; however, a weak possibility of bcc structure in Mn 15 is found. The calculated magnetic moment of Mn 15 is, however, found to be too large compared with the experimental result.

A Theoretical Study on the Pressure Dependence of the Band Gap in ${\rm A^{I}B^{III}C^{VI}_2}$ Compounds

The self-consistent scalar relativistic band structure for AgGaX 2 (X = S, Se, Te) performed in chalcopyrite structure using the TBLMTO method at various pressures are reported here. Empty spheres were introduced in the calculations as the chalcopyrite structure is loosely packed. From the total energy calculations, the equilibrium lattice constant and the bulk modulus at zero pressure were calculated and these values agree well with the reported experimental values. All these compounds are found to have direct energy gap at ambient pressure with the gap widening with increased pressures which are in agreement with the experimental results. The deformation potential, dE g /dP for the compounds are also reported here. The metallisation volumes are calculated and the possibility of observing superconductivity in these compounds is discussed.

Electronic Structure, Pressure Dependence and Optical Properties of FeS2

ABSTRACTA revisited electronic structure study of iron pyrite, FeS2, has been performed using a new Tight-Binding Linear Muffin-Tin Orbital (TB-LMTO) technique in which the radii of overlapping MT spheres are determined from a full potential construction. The interstitial spheres were chosen to provide an efficient packing of space while ensuring that the overlap between the spheres remain small. We have found that this treatment of interstitial spheres results in a dramatic improvement in the description of the electronic structure and the binding energy curves for FeS2 in comparison with a previous LMTO calculation. In particular, the energy band gap, the equilibrium lattice constant and the bulk modulus are all in much better agreement with experimental observations. Moreover, the calculated equation of state is in excellent accord with recent measured P- V data up to pressures of 15GPa with overall deviations of less than 10%. The predicted reflectivity spectrum of FeS2 as a function of pressure gives the observed behaviour of the optical edge. The bonding behaviour the orthorhombic marcasite phase of FeS2 is also discussed within this new TB-LMTO formalism.

INSULATOR-TO-METAL TRANSITION IN LaRhO3 UNDER HIGH PRESSURE

The band structure calculations of perovskite transition metal compound LaRhO 3 performed using 'tight binding linear muffin tin orbital' (TB-LMTO) method within local density approximation (LDA) under ambient and high pressures are reported here. Our calculations are able to successfully explain the insulating nature of the system and the insulator-to-metal transition (IMT) is observed for the reduced volume of 0.90. The first electronic structure calculation reported here for LaRhO 3 enables us to compare it with that of LaCoO 3 which brings out the role played by the d bands. These studies lead to distinguish between these two insulating systems and LaCoO 3 is found to be a charge transfer (CT) insulator which is in agreement with the recent experimental observations whereas LaRhO 3 is a conventional band insulator. Further, the equilibrium lattice constant, bulk modulus, its first derivative, and metallization volume obtained from the total energy calculations for expanded and reduced cell volumes are also reported for LaRhO 3.

Ab-Initio Calculations of the Electronic Structure and Properties of Titanium Carbosulfide

Titanium carbosulfide (Ti2CS) is frequently found as an inclusion phase in Ti - containing steels. It is of considerable interest because, whenever present in preference to the more common manganese sulfide (MnS), it significantly improves the toughness (a very desirable property) of the steel. Currently, to the best of our knowledge, there is no data, either computational or experimental, regarding the structural properties of Ti2CS. This data is needed to understand the influence of the Ti2CS inclusions on the toughness of the host material.In this paper, our results from the ab-initio calculations, using the LKKR-ASA (Layer Korringa Kohn Rostoker method in the Atomic Spheres Approximation) on the equilibrium ground state properties of bulk Ti2CS are presented and discussed. In particular, attention is focused upon (a) the Energy – Atomic Volume curve generated to calculate the equilibrium lattice constant and the bulk modulus, and (b) the density of states calculations. The application of these results to the subsequent study of an interface involving the carbosulfide and the host matrix is also illustrated.