Insight into the structure dependence on physical properties of the high temperature ceramics TaB2 boride
TL;DR: In this article, the first-principles method is used to investigate the structural stability, elastic properties, elastic anisotropy, electronic properties and thermodynamics properties for TaB2 boride with six possible structures.
About: This article is published in Vacuum.The article was published on 2020-07-01. It has received 21 citations till now. The article focuses on the topics: Boride & Anisotropy.
Citations
More filters
TL;DR: In this paper, the influence of noble metals on the electronic and optical properties of monoclinic Zirconium dioxide (ZrO2) was investigated, where three noble metals: Ru, Pd and Pt were considered as the doped element.
66 citations
TL;DR: In this paper, the structural, electronic and optical properties of ZrO are studied by the first-principles calculations, and they further study the influence of Ag and Cu on the electronic, optical and physical properties of zirconium oxides.
54 citations
01 Jul 2022
TL;DR: The ground state structure, electronic and optical properties of Zr3O are unclear until now as mentioned in this paper , and the authors apply the first-principles calculations to study the structure and electronic properties of three Zr-O oxides: rhombohedral (R32, R-3c) and hexagonal (P6322) phase.
Abstract: Zirconium oxides (Zr-O) has been widely used in energy storage system, catalyst, microelectronic, optoelectronics, and high-temperature ceramics etc. Unfortunately, the ground state structure, electronic and optical properties of Zr3O are unclear until now. Here, we apply the first-principles calculations to study the structure, electronic and optical properties of Zr3O. Three Zr3O oxides: rhombohedral (R32), rhombohedral (R-3c) and hexagonal (P6322) phase are studied. The results show that three Zr3O oxides are thermodynamic and dynamical stabilities. The calculated phonon density of state (PhDOS) further demonstrates the stable of Zr3O oxides. In particular, it is found that the rhombohedral (R-3c) Zr3O is slightly more stable than the other two Zr3O oxides. Unlike ZrO2, the Zr3O oxides exhibit better electronic properties due to the electronic jump between Zr- excitation band and Zr- conduction band near the Fermi level. Compared to the hexagonal Zr3O, the host peak of the rhombohedral Zr3O move into the low energy region, which leads to the red shift phenomenon occurs. In addition, it is found that the rhombohedral (R32, No.155) Zr3O oxide has better storage optical properties compared to the other two Zr3O oxides.
51 citations
TL;DR: In this paper, the effect of vacancy and oxygen occupation on the elastic properties and brittle-or-ductile behavior on Mo5Si3 was investigated by means of first-principles calculations, and it was found that Mo-Va2 vacancy has the stronger structural stability in the ground state in comparison with other vacancies.
Abstract: Improving brittle behavior and mechanical properties is still a big challenge for high-temperature structural materials. By means of first-principles calculations, in this paper, we systematically investigate the effect of vacancy and oxygen occupation on the elastic properties and brittle-or-ductile behavior on Mo5Si3. Four vacancies (Si–Va1, Si–Va2, Mo–Va1, Mo–Va2) and oxygen occupation models (O–Mo1, O–Mo2, O–Si1, O–Si2) are selected for research. It is found that Mo–Va2 vacancy has the stronger structural stability in the ground state in comparison with other vacancies. Besides, the deformation resistance and hardness of the parent Mo5Si3 are weakened due to the introduction of different vacancy defects and oxygen occupation. The ratio of B/G indicates that oxygen atoms occupation and vacancy defects result in brittle-to-ductile transition for Mo5Si3. These vacancies and the oxygen atoms occupation change the localized hybridization between Mo–Si and Mo–Mo atoms. The weaker O–Mo bond is a contributing factor for the excellent ductile behavior in the O-Si2 model for Mo5Si3.
50 citations
TL;DR: In this article, the magnetic properties and magnetocaloric effect of an antiferromagnetic/ferromagnetic (AFM/FM) BiFeO3/Co bilayer with mixed-spin (5/2, 3/2) have been studied based on Monte Carlo simulation.
Abstract: The magnetic properties and magnetocaloric effect of an antiferromagnetic/ferromagnetic (AFM/FM) BiFeO3/Co bilayer with mixed-spin (5/2, 3/2) have been studied based on Monte Carlo simulation. The magnetization, susceptibility, and critical temperature are investigated under various exchange couplings and an external magnetic field. In particular, the influence of exchange couplings and an external magnetic field on the magnetic entropy change, adiabatic temperature change, and the relative cooling power (RCP) are studied. The simulation results indicated that the decrease of the exchange coupling and the increase of external magnetic fields can cause an increase of magnetic entropy change, adiabatic temperature change, and RCP. In addition, the hysteresis loops of the system are presented for different exchange couplings and temperatures.
22 citations
References
More filters
TL;DR: An efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set is presented and the application of Pulay's DIIS method to the iterative diagonalization of large matrices will be discussed.
Abstract: We present an efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrices will be discussed. Our approach is stable, reliable, and minimizes the number of order ${\mathit{N}}_{\mathrm{atoms}}^{3}$ operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special ``metric'' and a special ``preconditioning'' optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calculations. It will be shown that the number of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order ${\mathit{N}}_{\mathrm{atoms}}^{2}$ scaling is found for systems containing up to 1000 electrons. If we take into account that the number of k points can be decreased linearly with the system size, the overall scaling can approach ${\mathit{N}}_{\mathrm{atoms}}$. We have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large number of different systems (liquid and amorphous semiconductors, liquid simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable. \textcopyright{} 1996 The American Physical Society.
81,985 citations
TL;DR: The basics of the suject are looked at, a brief review of the theory is given, examining the strengths and weaknesses of its implementation, and some of the ways simulators approach problems are illustrated through a small case study.
Abstract: First-principles simulation, meaning density-functional theory calculations with plane waves and pseudopotentials, has become a prized technique in condensed-matter theory. Here I look at the basics of the suject, give a brief review of the theory, examining the strengths and weaknesses of its implementation, and illustrating some of the ways simulators approach problems through a small case study. I also discuss why and how modern software design methods have been used in writing a completely new modular version of the CASTEP code.
9,350 citations
01 May 1952
TL;DR: The connection between the elastic behavior of an aggregate and a single crystal is considered in this article, with special reference to the theories of Voigt, Reuss, and Huber and Schmid.
Abstract: The connection between the elastic behaviour of an aggregate and a single crystal is considered, with special reference to the theories of Voigt, Reuss, and Huber and Schmid. The elastic limit under various stress systems is also considered, in particular, it is shown that the tensile elastic limit of a face-centred aggregate cannot exceed two-thirds of the stress at which pronounced plastic distortion occurs.
7,944 citations
4,690 citations
TL;DR: Tantalum diboride (TaB 2 ) was synthesized by reducing Ta 2 O 5 using B 4 C and graphite at 1600-°C under flowing Ar. The powder had an average particle size of 0.4μm with both needle-like and rounded particles as discussed by the authors.
119 citations