The electronic properties of two spinels Fe$_3$O$_4$ and Fe$_2$SiO$_4$ are studied by the density functional theory. The local Coulomb repulsion $U$ and the Hund's exchange $J$ between the $3d$ electrons on iron are included. For $U=0$, both spinels are half-metals, with the minority $t_{2g}$ states at the Fermi level. Magnetite remains a metal in a cubic phase even at large values of $U$. The metal-insulator transition is induced by the $X_3$ phonon, which lowers the total energy and stabilizes the charge-orbital ordering. Fe$_2$SiO$_4$ transforms to a Mott insulating state for $U>2$ eV with a gap $Δ_g\sim U$. The antiferromagnetic interactions induce the tetragonal distortion, which releases the geometrical frustration and stabilizes the long-range order. The differences of electronic structures in the high-symmetry cubic phases and the distorted low-symmetry phases of both spinels are discussed.
Electronic and magnetic properties of NiS_{2-x}Se_x: a comparative study
用密度泛函理论研究了黄铁矿系统NiS_{2-x} Se_x在压力下的金属-绝缘体转变和d电子离域问题.我们测试了几个近似，包括广义梯度近似（GGA），GGA+U的方法，和混合泛函。此外，我们应用GW近似和执行Hartree-Fock计算。硫族二聚体在电子结构中的重要作用在GGA中进行了讨论，GGA充分描述了晶格在金属-绝缘体转变中的作用。此外，还测定了磁相图。然而，电子性质的描述不充分-绝缘基态的NiS_2不能得到-和磁序略有高估。如果在GGA+U中考虑相关性，则发现绝缘体，但掺杂样品的非磁性基态不可接近。混合Fock交换与局部近似GGA正确地再现绝缘基态NiS_2，和金属基态掺杂和压力。绝缘体是-与早期的建议相反-莫特类型，即。e. Ni 3d {eg}态之间的能隙打开。由于Fock项，磁序被严重高估。所用的GW计算不能修正NiS_2的金属特性，也不能将能隙低估一个数量级。
A comparative study of different exchange-correlation functionals in understanding structural, electronic and thermoelectric properties of Fe$_{2}$VAl and Fe$_{2}$TiSn compounds
Crystalline black nitrogen (BN) is an allotrope of nitrogen with the black phosphorus (BP) structure recently synthesized at high pressure by two independent research groups [Ji et al., Sci. Adv. 6, eaba9206 (2020); Laniel et al., Phys. Rev. Lett. 124, 216001 (2020)]. Here, we present a systematic study of the electronic and optical properties of BN focusing on its comparison with BP. To this end, we use the state-of-the-art quasiparticle self-consistent $GW$ approach with vertex corrections in both the electronic and optical channels. Despite many similarities, the properties of BN are found …
Self-consistent evaluation of effective Coulomb interaction of V atom and its importance to understand the comparative electronic behaviour of vanadium spinels
本工作中，我们试图理解V原子局域电子之间的有效库仑相互作用（$U_{ef}$）对理解AV $_{2}$ O $_{4}$（A=Zn，Cd，Mg）化合物的比较电子行为的重要性。计算这些化合物的$U_{ef}$时，杂质V原子的$d$线性化能（$E_{d}$）的合适值为$\geq$（Fermi能级以上44.89 eV）。对应于$E_{d}$的这些值，ZnV $_{2}$ O $_{4}$、MgV $_{2}$ O $_{4}$和CdV $_{2}$ O $_{4}$的有效$U_{LSDA}$（$U_{PBEsol}$）的自洽计算值分别为$\sim$ 5.73（$\sim$ 5.92）、$\sim$ 6.06（$\sim$ 6.22）和$\sim$ 5.59（$\sim$ 5.71）eV。计算的$\frac{t}{U_{ef}}$（$t$是相邻位置之间的转移积分）的值随着从CdV $_{2}$ O $_{4}$到MgV $_{2}$ O $_{4}$到ZnV $_{2}$ O $_{4}$的V-V距离的减小而增加，并且发现与实验报道的带隙一致。ZnV $_{2}$ O $_{4}$、MgV $_{2}$ O $_{4}$和CdV $_{2}$ O $_{4}$的$\frac{t}{U_{ef}}$值分别为$\sim$ 0.023、$\sim$ 0.020和$\sim$ 0.018。因此，C…
Electronic structure study of vanadium spinels by using density functional theory and dynamical mean field theory
在理论上，AV $_{2}$ O $_{4}$（A=Zn，Cd和Mg）尖晶石的各种物理性质在过去的15年中得到了广泛的研究。除此之外，还没有对这些化合物进行系统的比较研究，其中使用了材料特定的参数。在这里，我们报告的比较电子行为的这些尖晶石通过使用组合的密度泛函理论和动力学平均场论，其中自洽计算库仑相互作用$U$和洪德的耦合$J$（由汤川筛选$λ$确定）被使用。观察到这些参数的主要特征，如绝缘带隙（$E_{g}$）、V3 $d$电子的巡游度和下Hubbard带的位置。ZnV $_{2}$ O $_{4}$的$E_{g}$计算值，发现CdV $_{2}$ O $_{4}$和MgV $_{2}$ O $_{4}$为$\sim$ 0.9eV，$\sim$ 0.95 eV和$\sim$ 1.15 eV，其中$E_{g}$的值接近ZnV $_{2}$ O $_{4}$和MgV $_{2}$ O $_{4}$。ZnV $_{2}$ O $_{4}$、CdV $_{2}$ O $_{4}$和MgV $_{2}$ O $_{4}$的Hubbard低带位置分别在$\sim$-1.05 eV、$\sim$-1.25 eV和$\sim$-1.15 eV附近，与ZnV $_{2}$ O $_{4}$的实验数据也符合得很好. V位平均杂质杂化函数的顺序为ZnV $_{2}$ O $_{4}$ $>$ MgV…
Comparative Raman study of Ruddlesden-Popper nickelates and the monolayer-trilayer polymorph
Max-Planck-Institute for Solid State Research（马克斯·普朗克固体的研究所）；Hefei National Laboratory（合肥国家实验室）；University of Science and Technology Beijing（北京科技大学）；University of Stuttgart（斯图加特大学）；Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）
Skyrmionic order and magnetically induced polarization change in lacunar spinel compounds GaV$_{4}$S$_{8}$ and GaMo$_{4}$S$_{8}$: comparative theoretical study
We study the many-body electronic structure of the stoichiometric and electron-doped trilayer nickelate Pr$_4$Ni$_3$O$_8$ in comparison to that of the stoichiometric and hole-doped infinite layer nickelate NdNiO$_2$ within the framework of density functional plus dynamical mean field theory, noting that Pr$_4$Ni$_3$O$_8$ has the same nominal carrier concentration as NdNiO$_2$ doped to a level of 1/3 holes/Ni. We find that the correlated Ni-$3d$ shells of both of these low valence nickelates have similar many-body configurations with correlations dominated by the $d_{x^2-y^2}$ orbital. Addition…
We present a comparative electronic structure study using DFT and various beyond-DFT (DFT+$U$, $G_0W_0$, DFT+DMFT) methods for ferromagnetic Iron (Fe) to find better approach for describing the spectral properties of correlated magnetic system. The computed value of $U$ ($W$) is $\sim$5.4 ($\sim$0.8) eV. The calculated spectra of all methods are providing good agreement with experimental spectra (ES) for peaks' positions. But, the proper line shape is only found from DFT+DMFT with correct estimation of incoherent states, which depends on $J$ and form of local Coulomb interactions. The estimati…
$J_{eff}$ states in a quasi one dimensional antiferromagnetic spin chain hexagonal Iridates Sr$_3$MIrO$_6$ (M=Mg, Zn, Cd): an $ab-initio$ comparative perspective
We present a comparative density-functional theory plus dynamical mean-field theory (DFT+DMFT) study of the two known superconducting members of the rare-earth (R) layered nickelate family: hole-doped RNiO$_{2}$ ($n=\infty$) and R$_{6}$Ni$_{5}$O$_{12}$ ($n=5$). At the same nominal carrier concentration, these two materials exhibit nearly identical electronic structures and many-body correlations effects: mass enhancements, self-energies, and occupations. However, the fermiology of the quintuple-layer nickelate is more two-dimensional-like than its infinite-layer counterpart making this new sup…
