共查询到20条相似文献,搜索用时 15 毫秒
1.
M3X (M=Cr, V; X=Si, Ge) compounds are studied using first-principles calculations based on the Density Functional Theory (DFT). It is found that the bulk of Cr3X (X=Si, Ge) compounds are comparable to those of Al2O3, the nearest-neighbor distance DM−M and DM−X in these compounds increase and the bulk modulus decrease, there is a strong interaction between M and M (M=Cr the interaction is stronger). Also the interaction between M (M=Cr, V) and X (X=Ge) is negative, an anti-bonding-type interaction is dominant between these atoms. 相似文献
2.
R.D. Eithiraj 《Journal of Physics and Chemistry of Solids》2011,72(4):227-232
First-principles calculations were performed to investigate the stability, electronic structure and magnetism in Group IV elements-doped alkali-metal oxides (M2O) [M: Li, Na, K, Rb] in antifluorite structure using the linear muffin-tin orbital method in its tight-binding representation (TB-LMTO). The calculations reveal that non-magnetic dopants can induce stable half-metallic ferromagnetic ground state in I2-VI compounds. Total energy calculations show that the ferromagnetic state is energetically more stable than the non-magnetic state at equilibrium volume. Ground state properties such as equilibrium lattice constant and bulk modulus were calculated. The magnetic moment is found to be 2.00 μB per dopant atom. 相似文献
3.
Hongzhi Luo Guodong Liu Fanbin Meng Jianqiang Li Enke Liu Guangheng Wu 《Journal of magnetism and magnetic materials》2012
The electronic structure and magnetic properties of new Fe-based Heusler alloys Fe2TiZ (Z = Ga, Ge, As, In, Sn and Sb) have been studied by first-principles calculations. In these alloys, the 24-electron Fe2TiGe, Fe2TiSn are nonmagnetic semiconductors and other compounds are all ferrimagnetic metals. Fe2TiAs and Fe2TiSb are predicted to be half-metals with 100% spin polarization. The spin polarization ratio in Fe2TiGa and Fe2TiIn is also quite high. The calculated total moment for Fe2TiAs and Fe2TiSb is 1 μB, which is mainly determined by the Fe partial moment. The half-metallicity of Fe2TiSb is stable under lattice distortion. The spin polarization of Fe2TiSb is found to be 100% for the lattice variation in a range of 5.6–6.1 Å, which is attractive in practical applications. 相似文献
4.
The electronic structure and magnetic properties of B-based Heusler alloys Fe2YB (Y=Ti, V, Cr and Mn) have been studied theoretically. These alloys are all ferrimagnets except for Fe2VB. The latter has 24 valence electrons and is a paramagnetic semimetal. Fe2CrB is predicted to be half-metals at equilibrium lattice constant. The spin polarization of Fe2MnB is also quite high. The calculated total moments are 1.00 μB for Fe2CrB and 2.04 μB for Fe2MnB. In Fe2CrB and Fe2MnB, the total moments are mainly determined by the partial moment of Cr or Mn. The Fe moment is relatively small and antiparallel to that of Cr or Mn. Under uniform lattice distortion, the half-metallicity of Fe2CrB is more stable than Fe2MnB, which is related to the detailed DOS structure of them near EF. 相似文献
5.
The periodic Hartree-Fock method has been applied to calculate the electronic structure of the yttrium aluminium garnet. We report on the results of the density of state calculations, the population analysis, as well as the electric-field-gradient distribution. A comparative analysis with the related structure α-Al2O3 was done. The calculations show that the Y3Al5O12 crystal is more ionic than α-Al2O3. 相似文献
6.
Density functional theory (DFT), is used in our calculations to study the V3M (M = Si, Ge and Sn) compounds, we are found that V3Sn compound is mechanically unstable because of a negative C44 = −19.41 GPa. For each of these compounds considered, the lowest energy structure is found to have the lowest N(Ef) value. Also there is a strong interaction between V and V, the interaction between M (M = Si, Ge, Sn) and V (M and M) is negative, not including Si [Sn]. In phonon density of states PDOS, the element contributions varies from lighter (high frequency) to heaviest (low frequency). 相似文献
7.
In this study, the electronic structure and magnetic properties of novel half-metallic Ti2FeSi full-Heusler compound with CuHg2Ti-type structure were examined by density functional theory (DFT) calculations. The electronic band structures and density of states of the Ti2FeSi compound show the spin-up electrons are metallic, but the spin-down bands are semiconductor with a gap of 0.45 eV, and the spin-flip gap is of 0.43 eV. Fe atom shows only a small magnetic moment and its magnetic moment is antiparallel to that of Ti atoms, which is indicative of ferrimagnetism in Ti2FeSi compound. The Ti2FeSi Heusler compound has a magnetic moment of 2 μB at the equilibrium lattice constant a=5.997 Å. 相似文献
8.
In this paper, we study the structural, electronic and elastic properties of the ternary AgSbTe2, AgSbSe2, Pr3AlC, Ce3AlC, Ce3AlN, La3AlC and La3AlN compounds using the full-potential linearized augmented plane wave (FP-LAPW) scheme and the pseudopotential plane wave (PP-PW) scheme in the frame of generalized gradient approximation (GGA). Results are given for the lattice parameters, bulk modulus, and its pressure derivative. The calculated lattice parameters are in good agreement with experimental results. We have determined the full set of first-order elastic constants, shear modulus, Young's modulus and Poisson's ratio of these compounds. Also, we have presented the results of the band structure, densities of states, it is found that this compounds metallic behavior, and a negative gap Г→R for Pr3AlC. The analysis charge densities show that bonding is of covalent–ionic and ionic nature for AgSbSe2 and AgSbTe2 compounds. 相似文献
9.
The first principles within the full potential linearized augmented plane wave (FP-LAPW) method was applied to study the structural and electronic properties of cubic perovskite-type compounds BiAlO3 and BiGaO3. The lattice constant, bulk modulus, its pressure derivative, band structure and density of states were obtained. The results show that BiGaO3 should exhibit higher hardness and stiffness than BiAlO3. The Al–O or Ga–O bonds are typically covalent with a strong hybridizations as well as Bi–O ones that have a significant ionic character. Both materials are weakly ionic and exhibit wide and indirect band gaps, which are typical of insulators. 相似文献
10.
The structural stability and electronic properties of Co2N, Rh2N and Ir2N were studied by using the first principles based on the density functional theory. Two structures were considered for each nitride, orthorhombic Pnnm phase and cubic Pa3¯ phase. The results show that they are all mechanically stable. Co2N in both phases are thermodynamically stable due to the negative formation energy, while the remaining two compounds are thermodynamically unstable. The calculated properties show that they are all metallic and non-magnetic. Ir2N at Pnnm phase is a potentially hard material. The bonding behavior is analyzed. 相似文献
11.
Yuki Obukuro Hiroyuki Nakamura Kenji Obata Shigenori Matsushima Masao Arai Kenkichiro Kobayashi 《Journal of Physics and Chemistry of Solids》2011,72(12):1477-1481
The electronic structure of Sr2Bi2O5 is calculated by the GGA approach. Both of the valence band maximum and the conduction band minimum are located at Γ-point. This means that Sr2Bi2O5 is a direct band-gap material. The wide energy-band dispersions near the valence band maximum and the conduction band minimum predict that holes and electrons generated by band gap excitation have a high mobility. The conduction band is composed of Bi 6p, Sr 4d and O 2p energy states. On the other hand, the valence band can be divided into two energy regions ranging from −9.5 to −7.9 eV (lower valence band) and from −4.13 to 0 eV (upper valence band). The former mainly consists of Bi 6s states hybridizing with O 2s and O 2p states, and the latter is mainly constructed from O 2p states strongly interacting with Bi 6s and Bi 6p states. 相似文献
12.
Electronic structure and properties of Fe6(N1−xCx)2 carbonitrides with 0≤x≤1, i.e. the concentrations of N and C elements are respectively in range of 0∼7.69 wt% and 0∼6.67 wt%, have been studied by first-principles calculations based on density functional theory (DFT) implemented in the Cambridge Serial Total Energy Package (CASTEP) code. The calculated results show that the Fe6(N1−xCx)2 carbonitrides are thermodynamically and mechanically stable. Lattice parameters and stability of the carbonitrides increase when C atoms replace N atoms in Fe6N2 unit cell. In Fe6(N1−xCx)2 unit cell, the hybridization effect between C-2p and Fe-3d states is stronger than that between N-2p and Fe-3d states. Elastic properties and melting points of the carbonitrides change slightly with the substitution of C atoms for N atoms in Fe6(N1−xCx)2 carbonitrides. 相似文献
13.
Hongzhi Luo Fanbin MengYanqiang Cai Wangwen HongEnke Liu Guangheng WuXiaoxi Zhu Chengbao Jiang 《Journal of magnetism and magnetic materials》2011,323(17):2323-2327
Quaternary Heusler alloys Fe1.5M0.5CoSi with M=V, Cr, Mn and Fe have been investigated theoretically and experimentally. All of these samples crystallize in the ordered Heusler-type structure. The calculated electronic structure shows a pseudogap around EF in the minority spin states of Fe2CoSi. With the substitution of low-valent atoms for Fe, the majority antibonding peak is shifted to higher energy and a minority gap around the Fermi level is opened. High spin polarization ratio is obtained in Fe1.5M0.5CoSi (M=V, Cr, Mn) alloys. The calculated total spin moments decrease with decreasing number of valence electrons and follow the Slater-Pauling curve, which agree with the experimental results well. The Curie temperature decreases as M atom varies from Fe to V, but is always higher than 650 K, which is suitable for technical applications. 相似文献
14.
自由基OH(X^П,A^2∑^+)的从头算研究 总被引:16,自引:0,他引:16
用分子轨道从头算方法,研究了OH分子的基态(X^П)和激发态(A^2∑^+)。结果表明,对于基态,在QCISD(T)/6—311++G(3df,3pd)理论水平上,键距是0.09704nm,与实验值0.09706nm完全吻合。对于激发态,使用完全活性空间方法(CASSCF)和大基组6—311++G(3df,3pd),键距是0.10098nm,与实验值0.10121nm基本吻合。从激发态A^2∑^+(v=0)到基态X^П(v=0)的垂直跃迁能量是4.4692eV,与实验值4.3980eV也吻合较好。 相似文献
15.
Ab initio calculations of lattice constants, lattice stabilities of HgX(X = S, Se, Te) at different electronic temperatures(T_e) have been performed within the density functional theory(DFT). We find that the lattice constants of HgX increase and the phonon frequencies reduce as T_e increases. Especially the transverse-acoustic(TA) phonon frequencies of HgX gradually become negative with the elevation of the electron temperature. That is to say ultrafast intense laser induces lattice instabilities of HgX and athermal melting appears for the increase of laser intensity. What is more, with the X atom number increasing, the critical electronic temperatures of HgX are decreased in sequence. This result would be helpful for understanding the athermal melting processes for femtosecond laser micromachining. 相似文献
16.
S. Kashida W. Shimosaka D. Yoshimura 《Journal of Physics and Chemistry of Solids》2003,64(12):2357-2363
The electronic structures of the copper chalcogenide compounds, Cu2S, Cu2Se and Cu2Te have been investigated by taking photoemission data with synchrotron photon sources. The band calculations are done using the full-potential linear-muffin-tin-orbital method. Since the crystal structures are not clarified well, several simplified structure models are used. The calculated densities of states are compared with the observed spectra. The analysis shows that a sharp peak at −3.5 eV is due to the Cu 3d states, and that the tails at the high and low energy sides of the Cu 3d peak are due to the chalcogen p states. 相似文献
17.
A theoretical study on the stabilities of the crystal structures of K2Al2B2O7 (KABO) and Na2Al2B2O7 (NABO) has been carried out using density functional theory with generalized-gradient corrections. All structures have been optimized by minimizing the total energies with respect to lattice constants and to the atomic coordinates within the unit cell. In the case of KABO, the structure with space group P321 always takes energy advantage over the whole volume range studied, whereas on both volume expansion and contraction, the original NABO structure becomes unstable, taking a structure transition from its space group to the P321 space group of KABO structure. The theoretical predictions were well realized in the experimental results on the structure changes of the (K1−xNax)2Al2B2O7 solid solution system. 相似文献
18.
The millimeterwave spectra of F210BOH and F211BOH (difluorohydroxyborane) have been measured in their ground vibrational state. Accurate rotational and centrifugal distortion constants have been determined. The equilibrium geometry and anharmonic force fields have been calculated at the CCSD(T) level of theory. The ab initio centrifugal distortion constants and rotation-vibration interaction constants are compared to the experimental values. Some discrepancies are found and discussed. Particularly, it is explained why the semi-experimental structure is not reliable. The best equilibrium structure is: re(BFcis) = 132.29 pm, re(BFtrans) = 131.29 pm, re(BO) = 134.48 pm, re(OH) = 95.74 pm, ∠e(FBF) = 118.36°, ∠e(FcisBO) = 122.25°, and ∠e(BOH) = 113.14°. 相似文献
19.
The first principles within the full potential linearized augmented plane wave (FP-LAPW) method was applied to study the compound of Cutp(OH2)2. The density of states, the electronic band structure and the spin magnetic moment are calculated. The calculations reveal that the compound has a ferromagnetic interaction arising from the bridging water molecule. The spin magnetic moment 1.0μB per molecule mainly comes from the Cu ion with little contribution from O, C anion. 相似文献
20.
运用基于密度泛函理论的第一性原理分子动力学和静态电子结构计算,研究了La65X35(X=Ni,Al)非晶合金体系原子结构随温度演化的规律及其相关电子结构特性.使用径向分布函数、Voronoi团簇以及键对分析等给出了从高温液体快速冷却到玻璃态过程中原子结构的演化规律.研究发现,该类合金体系的原子排布符合局域密堆模型,两体系中占比最大的特征多面体类型由溶质与溶剂原子半径比调控;两体系中高五次对称性局域结构随温度的下降而增加验证了其在抑制晶化方面的重要作用;利用投影态密度分析两体系电子结构之间的差异,指出La-5d与Ni-3d电子间强烈的杂化是La–Ni 间键长缩短的电子结构起源,为理解成分相关的结构和物性提供了重要线索. 相似文献