The modified Becke-Johnson exchange potential combined with local-density approximation correlation (mBJLDA) has recently attracted interest because it provides highly improved band gaps at a very low computational cost. In this work we performed an extensive investigation of the performance of the mBJLDA potential employing a norm-conserving pseudopotential plane-waves approach (mBJLDA@PP), as implemented in the abinit code, using a test set of 83 solids representing a wide range of semiconductors and insulators. Our results confirm the conclusion of our previous study that the number of electrons treated as valence in the pseudopotentials of the cations can have a significant impact on the calculated mBJLDA@PP band gaps. More specifically, while the use of typical pseudopotentials leads to accurate band gaps of certain systems, it yields significantly underestimated band gaps for other systems compared to experiment and to those of the all-electron mBJLDA (mBJLDA@AE) approach. The classes of the latter systems are identified, and this problem is resolved by including some outer core states as valence. The resulting mean absolute error in the calculated band gaps (compared to experiment) is of 0.46 eV, which is comparable to that of the mBJLDA@AE band gaps, reflecting the accuracy and reliability of the mBJLDA@PP approach for the band gap calculations.
We extend the Vanderbilt ultrasoft pseudopotential scheme by adding kinetic energy density terms, in order to use meta-GGA exchange potentials, such as the Becke-Johnson or Tran-Blaha potentials, in the planewave-pseudopotential implementation of Density Functional Theory. Having implemented kinetic energy augmentation and non-linear core correction terms in the CASTEP density functional package, we evaluate the validity of our approach by comparing the calculated electronic structure of isolated atoms and semiconductor crystals to all-electron benchmark calculations. Based on our results, we …
We report first-principles calculations, within density functional theory, on the lead halide compounds PbCl2, PbBr2, and CH3NH3PbBr3-xClx, taking into account spin-orbit coupling. We show that, when the modified Becke-Johnson exchange potential is used with a suitable choice of defining parameters, excellent agreement between calculations and experiment is obtained. The computational model is then used to study the effect of replacing the methylammonium cation in CH3NH3PbI3 and CH3NH3PbBr3 with either N2H+5 or N2H+3, which have slightly smaller ionic radii than methylammonium. We predict that…
Recently in the Wien2k code, the modified Becke-Johnson potential (mBJLDA) was implemented. As the authors [{\em Phys.Rev.Lett.} 102, 226401 (2009)] point, this potential reproduces the band gap of semiconductors with improved accuracy. In this paper we present our analysis of this potential in two directions. First, we checked whether this potential reproduces the band structure for metals, an analysis that lacked in the literature. We calculated the band gap of a group of semiconductors. We observed that the Linear Density Approximation (LDA) give rise to a shorter lattice constant as compar…
In this work we use density functional theory (DFT) to investigate the influence of semi-local exchange and correlation effects on the electronic and optical properties of zinc oxide. We find that the inclusion of such effects using the Tran-Blaha modified Becke-Johnson potential yields an excellent description of the electronic structure of this material giving energy band gap which is systematically larger than the one obtained with standard local functionals such as the generalized gradient approximation. The discrepancy between the experimental and theoretical band gaps is then significant…
The stability, electronic structure, optical and thermoelectric properties of Te-doped BaTiO3 are investigated by first-principal calculation based on the density functional theory and Boltzmann transport theory implemented in WIEN2K and BoltzTraP simulation program. This study is carried out by applying LDA + TB-mBJ potential. Formation energy of each doped structure is calculated to examine the stability and feasibility of the synthesis. Incorporating Te into BaTiO3 efficiently reduces the electronic band gap and the level of band gap reduction can be controlled by varying the amount of dopa…
In this paper, we have performed first principles calculations to study optoelectronic, thermodynamic and transport properties of Fe2TiGe using density functional theory (DFT). The semi-classical Boltzmann transport theory is used to investigate transport properties. The calculated energy bands indicate that Fe2TiGe is an indirect band gap semiconductor with band gap 0.734 eV for TB-mBJ functional. Fe-3d and Ti-3d orbitals have the dominant contributions to the density of states due to strong hybridization between them. The maximum value of absorption coefficient is found to be 224x10^4 cm-1 i…
We calculate the mirror Chern number (MCN) and the band gap for the alloy Pb1-xSnxSe as a function of the concentration x by using virtual crystalline approximation. We use the electronic structure from the relativistic density functional theory calculations in the Generalized-Gradient- Approximation (GGA) and meta-GGA approximation. Using the modified Becke-Johnson meta- GGA functional, our results are comparable with the available experimental data for the MCN as well as for the band gap. We advise to use modified Becke-Johnson approximation with the parameter c=1.10 to describe the transiti…
An asymptotic corrected exchange hole potential analogous to Becke-Roussel [A. D. Becke and M. R. Roussel, Phys. Rev. A 39, 3761 (1989)] is constructed by modeling the exchange hole using the generalized coordinate transformation based on density matrix expansion. The model potential is Laplacian free and the inhomogeneity present in the system is included in the momentum vector without affecting the uniform density limit. The parameters associated with the model exchange hole are fitted with the spherical atoms. The newly constructed potential along with Tran-Blaha modified Becke-Johnson (TBM…
We have performed systematic first principles study of the electronic structure and band topology properties of $LnPn$ compounds ($Ln$=Ce, Pr, Gd, Sm, Yb; $Pn$=Sb, Bi). Assuming the $f$-electrons are well localized in these materials, both hybrid functional and modified Becke-Johnson calculations yield electronic structure in good agreement with experimental observations, while generalized gradient approximation calculations severely overestimate the band inversions. From Ce to Yb, a systematic reduction of band inversion with respect to the increasing $Ln$ atomic number is observed, and $\mat…
Electronic structure and optical band gap determination of NiFe2O4
在理论研究中，我们调查的电子结构和带隙的反尖晶石型铁氧体NiFe 2 O 4。通过在修正的Becke-Johnson势中拟合Tran-Blaha参数，精确地再现了实验的光吸收谱。通常应用的Tauc图找到的光学间隙的准确性进行评估的基础上计算的光谱，我们发现，这种方法可能会导致误解的实验数据。NiFe_2 O_4的最小带隙为1.53eV宽的间接带隙，位于少数自旋通道中。
The structural and electronic properties of zinc-blende (ZB) GaAs were calculated within the framework of plane wave density-functional theory (DFT) code JDFTx by using Becke 86 in 2D and PBE exchange correlation functionals from libXC. The standard optimized norm-conserving Vanderbilt pseudopotentials were used to calculate optimized lattice constant, band gap and spin-orbit split-off parameter. The calculated values of optimized lattice constant and direct band gap are in satisfactory agreement with other published theoretical and experimental findings. By including spin-orbit (SO) coupling,…
We use the modified Becke-Johnson exchange potential (mBJ) with the spin-orbit coupling effect (SOC) to study effects of biaxial strain and local constant potential on electronic structure of monolayer SnSe. Our results show the fundamental band gap size can be tuned via biaxial strain. Compressive strain (tensile strain) can narrow (enlarge) band gap, and compressive strain causes the transition from quasi-direct to indirect band gap. Moreover, considering that any tuning of electronic structure is realized by changing the periodic potential distribution in the crystalline, we directly add co…
We report on optical properties of various polymorphs of hafnia predicted within the framework of density functional theory. The full potential linearised augmented plane wave method was employed together with the Tran-Blaha modified Becke-Johnson potential for exchange and local density approximation for correlation. Unit cells of monoclinic, cubic, and tetragonal crystalline, and a simulated annealing-based model of amorphous hafnia were fully relaxed with respect to internal positions and lattice parameters. The thus obtained band gaps of 5.76 eV, 5.88 eV, 6.54 eV, and 5.5 eV for monoclinic…
Kohn-Sham (KS) density functional theory (DFT) is a very efficient method for calculating various properties of solids as, for instance, the total energy, the electron density, or the electronic band structure. The KS-DFT method leads to rather fast calculations, however the accuracy depends crucially on the chosen approximation for the exchange and correlation (xc) functional $E_{\text{xc}}$ and/or potential $v_{\text{xc}}$. Here, an overview of xc methods to calculate the electronic band structure is given, with the focus on the so-called semilocal methods that are the fastest in KS-DFT and …
In this research paper, we investigated the structural, electronic, and magnetic features of titanium atom substituting calciumatom in rock salt structure of CaS to explore the new dilute magnetic semiconductor compounds. The calculations are carried out using the full potential linearized augmented plane wave (FP-LAPW) method based on spin-polarized density functional theory, implemented in WIEN2k code. The generalized gradient approximation and Tran-Balaha modified Becke-Johnson exchange potential. The stability of Ti doped CaS in ferromagnetic state is provided by the total energy released …
Prediction model of band-gap for AX binary compounds by combination of density functional theory calculations and machine learning techniques
利用Kohn-Sham带隙和其他组成元素和晶体结构的基本信息作为预测因子，应用机器学习技术建立了156 AX二元化合物G 0 W 0带隙的预测模型。普通最小二乘回归（OLSR），最小绝对收缩和选择算子（LASSO）和非线性支持向量回归（SVR）方法被应用于多个水平的预测集。当用GGA（PBE）或修正的Becke-Johnson（mBJ）的Kohn-Sham带隙作为单一预测因子时，OLSR模型预测了随机选取的测试数据的G 0 W 0带隙，均方根误差（RMSE）为0.54 eV。当通过PBE和mBJ方法的Kohn-Sham带隙与一组代表组成元素和晶体结构的各种形式的预测因子一起使用时，RMSE显著降低。SVR的最佳模型产生0.18 eV的RMSE。以这种方式估计的一组大的带隙应该是有用的材料探索的预测。
We employ first-principles techniques tailored to properly describe semiconductors (modified Becke-Johnson potential added to the exchange-correlation functional), to obtain the electronic band structures of both the zinc-blende and wurtzite phases of GaAs, GaSb, InAs, and InSb. We extract the spin-orbit fields for the relevant valence and conduction bands at zone center, by fitting the spin-splittings resulting from the lack of space inversion symmetry of these bulk crystal structures, to known functional forms---third-order polynomials. We also determine the orientations of the spin-orbit ve…
The thermoelectric properties of halide perovskites $\mathrm{CsMI_3}$ (M=Sn and Pb) are investigated from a combination of first-principles calculations and semiclassical Boltzmann transport theory by considering both the electron and phonon transport. The electronic part is performed using a modified Becke and Johnson (mBJ) exchange potential, including spin-orbit coupling (SOC), while the phonon part is computed using generalized gradient approximation (GGA). It is found that SOC has remarkable detrimental effect on n-type power factor, while has a negligible influence in p-type doping, whic…
Based on the work of Gritsenko et al. (GLLB) [Phys. Rev. A 51, 1944 (1995)], the method of Kuisma et al. [Phys. Rev. B 82, 115106 (2010)] to calculate the band gap in solids was shown to be much more accurate than the common local density approximation (LDA) and generalized gradient approximation (GGA). The main feature of the GLLB-SC potential (SC stands for solid and correlation) is to lead to a nonzero derivative discontinuity that can be conveniently calculated and then added to the Kohn-Sham band gap for a comparison with the experimental band gap. In this work, a thorough comparison of G…
Accurate theoretical prediction of the band offsets at interfaces of semiconductor heterostructures can often be quite challenging. Although density functional theory has been reasonably successful to carry out such calculations and efficient and accurate semilocal functionals are desirable to reduce the computational cost. In general, the semilocal functionals based on the generalized gradient approximation (GGA) significantly underestimate the bulk band gaps. This, in turn, results in inaccurate estimates of the band offsets at the heterointerfaces. In this paper, we investigate the performa…
Equilibrium crystal structures, electron band dispersions and band gap values of layered GaSe and InSe semiconductors, each being represented by four polytypes, are studied via first-principles calculations within the density functional theory (DFT). A number of practical algorithms to take into account dispersion interactions are tested, from empirical Grimme corrections to many-body dispersion schemes. Due to the utmost technical accuracy achieved in the calculations, nearly degenerate energy-volume curves of different polytypes are resolved, and the conclusions concerning the relative stabi…
We present and compare three distinct atomistic models -- based on first principles and semi-empirical approaches -- of the structural and electronic properties of Ge$_{1-x}$Sn$_{x}$ alloys. Density functional theory calculations incorporating Heyd-Scuseria-Ernzerhof (HSE) and modified Becke-Johnson (mBJ) exchange-correlation functionals are used to perform structural relaxation and electronic structure calculations for a series of Ge$_{1-x}$Sn$_{x}$ alloy supercells. Based on HSE calculations, a semi-empirical valence force field (VFF) potential and $sp^{3}s^{\ast}$ tight-binding (TB) Hamilto…
Computational study of structural, electronic and optical properties of crystalline NH$_4$N$_3$
采用基于密度泛函理论（DFT）的平面波赝势（PW-PP）方法，对正交晶系叠氮铵（NH $_4$ N $_3$）的结构、电子、成键和光学性质进行了系统的计算研究.半经验色散修正方案已被用来解释分子晶体NH $_4$ N $_3$中的非键相互作用。用色散修正方法得到的基态晶格参数和分数坐标与实验结果吻合得很好。我们计算了NH-$_4$-$_3$的单晶弹性常数，并通过观察到的弹性常数（C $_{33}$ $>$ C $_{11}$ $>$ C $_{22}$）的顺序解释了它的敏感性.采用全势线性缀加平面波（FP-LAPW）方法和最近开发的Tran-Blaha修正Becke-Johnson（TB-mBJ）势泛函计算了电子结构和光学性质。TB-mBJ电子结构表明NH $_4$ N $_3$是直接带隙绝缘体，带隙为5.08 eV，而用标准广义梯度近似计算的带隙为4.10 eV。通过计算三种不同晶轴方向的介电函数和折射率等光学常数，分析了晶体的光学各向异性。吸收光谱表明，NH $_4$ N $_3$对紫外光敏感。此外，我们还分析了NH $_4$ N $_3$的爆轰特性使用报告的生成热和计算的密度。用Kamlet-Jacobs经验公式计算得到NH $_4$ N $_3$的爆速为6.45 km/s，爆压为15.16 GPa。
The electronic structure of the rare-earth mononitrides LnN (where Ln=rare-earth), which are promising materials for future spintronics applications, is difficult to resolve experimentally due to a strong influence of defects on their transport and optical properties. At the same time, LnN are challenging for theory, since wide semiconducting/semimetallic 2p and 5d bands need to be described simultaneously with strongly correlated 4f states. Here, we calculate the many-body spectral functions and optical gaps of a series of LnN (with Ln= Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er) by a density-functional+…
The accuracy of effective masses predicted by density functional theory depends on the exchange-correlation functional employed, with nonlocal hybrid functionals giving more accurate results than semilocal functionals. In this article, we benchmark the performance of the Perdew-Burke-Ernzerhof (PBE), Tran-Blaha modified Becke-Johnson (TB-mBJ), and the hybrid Heyd-Scuseria-Ernzerhof (HSE06) exchange-correlation functionals and potentials for the calculation of effective masses with perturbation theory. We introduce the mstar60 dataset, which contains 60 effective masses derived from 18 semicond…
The electronic band structure of Ga(PAsN) with a few percent of nitrogen is calculated in the whole composition of Ga(PAs) host using the state-of-the-art density functional methods including the modified Becke-Johnson functional to correctly reproduce the band gap, and band unfolding to reveal the character of the bands within the entire Brillouin zone. As expected, relatively small amounts of nitrogen introduced to Ga(PAs) lead to formation of an intermediate band below the conduction band which is consistent with the band anticrossing model, widely used to describe the electronic band struc…
