In this paper we calculated the elastic constants of $gamma Ce$. The calculations were performed self-consistently using the full potential augmented plane wave plus local orbital (FP-APW+lo) method. We used the generalized gradient approximation (GGA) to calculate the exchange-correlation energy. The elastic constants were obtained from the second order derivatives of energy with respect to lattice parameters. In this work we introduced a method to impose a deformation to the primary structure to simplify our calculations changing an fcc structure to bct.
We have carried out a first principles study of the elastic properties and electronic structure for two room-temperature stable Pt silicide phases, tetragonal alpha-Pt_2Si and orthorhombic PtSi. We have calculated all of the equilibrium structural parameters for both phases: the a and c lattice constants for alpha-Pt_2Si and the a, b, and c lattice constants and four internal structural parameters for PtSi. These results agree closely with experimental data. We have also calculated the zero-pressure elastic constants, confirming prior results for pure Pt and Si and predicting values for the six (nine) independent, non-zero elastic constants of alpha-Pt_2Si (PtSi). These calculations include a full treatment of all relevant internal displacements induced by the elastic strains, including an explicit determination of the dimensionless internal displacement parameters for the three strains in alpha-Pt_2Si for which they are non-zero. We have analyzed the trends in the calculated elastic constants, both within a given material as well as between the two silicides and the pure Pt and Si phases. The calculated electronic structure confirms that the two silicides are poor metals with a low density of states at the Fermi level, and consequently we expect that the Drude component of the optical absorption will be much smaller than in good metals such as pure Pt. This observation, combined with the topology found in the first principles spin-orbit split band structure, suggests that it may be important to include the interband contribution to the optical absorption, even in the infrared region.
The temperature anomalies in the Earths mantle associated with thermal convection1 can be inferred from seismic tomography, provided that the elastic properties of mantle minerals are known as a function of temperature at mantle pressures. At present, however, such information is difficult to obtain directly through laboratory experiments. We have therefore taken advantage of recent advances in computer technology, and have performed finite-temperature ab initio molecular dynamics simulations of the elastic properties of MgSiO3 perovskite, the major mineral of the lower mantle, at relevant thermodynamic conditions. When combined with the results from tomographic images of the mantle, our results indicate that the lower mantle is either significantly anelastic or compositionally heterogeneous on large scales. We found the temperature contrast between the coldest and hottest regions of the mantle, at a given depth, to be about 800K at 1000 km, 1500K at 2000 km, and possibly over 2000K at the core-mantle boundary.
We report on measurements of the adiabatic second order elastic constants of the off-stoichiometric Ni$_{54}$Mn$_{23}$Al$_{23}$ single crystalline Heusler alloy. The variation in the temperature dependence of the elastic constants has been investigated across the magnetic transition and over a broad temperature range. Anomalies in the temperature behaviour of the elastic constants have been found in the vicinity of the magnetic phase transition. Measurements under applied magnetic field, both isothermal and variable temperature, show that the value of the elastic constants depends on magnetic order, thus giving evidence for magnetoelastic coupling in this alloy system.
In this work, we present the program MAELAS to calculate magnetocrystalline anisotropy energy, anisotropic magnetostrictive coefficients and magnetoelastic constants in an automated way by Density Functional Theory calculations. The program is based on the length optimization of the unit cell proposed by Wu and Freeman to calculate the magnetostrictive coefficients for cubic crystals. In addition to cubic crystals, this method is also implemented and generalized for other types of crystals that may be of interest in the study of magnetostrictive materials. As a benchmark, some tests are shown for well-known magnetic materials.
Optical and electrical properties of two-dimensional transition metal dichalcogenides (TMDCs) grown by chemical vapor deposition (CVD) are strongly determined by their microstructure. Consequently, the visualization of spatial structural variations is of paramount importance for future applications. Here we demonstrate how grain boundaries, crystal orientation, and strain fields can unambiguously be identified with combined lateral force microscopy (LFM) and transverse shear microscopy (TSM) for CVD-grown tungsten disulfide (WS2) monolayers, on length scales that are relevant for optoelectronic applications. Further, angle-dependent TSM measurements enable us to acquire the fourth-order elastic constants of monolayer WS2 experimentally. Our results facilitate high-throughput and nondestructive microstructure visualization of monolayer TMDCs, insights into their elastic properties, thus providing an accessible tool to support the development of advanced optoelectronic devices based on such two-dimensional semiconductors.