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本文借助于一种改进的薄膜LAPW(线性迭加平面法)的基函数描写方法以及薄膜jellium-slab模型计算了具有三层slab的C_s-W吸附系统的功函数,得到了一组与实验更为符合的结果,即清洁表面功函数是4.89eV(近期计算值是5.4eV),这与S.Ohnishi等计算的结果(三层4.82eV,五层4.62eV,七层4.64eV,九层4.58eV)一致,功函数约在θ_1≈0.21处取极小值,其值为1.35eV,较近期结果(约0.8eV)与实验值(1.77eV)更为接近。本文着重分析了φ-θ曲线的形成与5d电子态变化及电子转移之间的关系. 相似文献
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C. Ambrosch-Draxl E. Y. Sherman H. Auer T. Thonhauser 《Journal of Superconductivity》2004,17(2):215-219
To understand the link between doping and electronic properties in the high-temperature superconductors, we have performed first-principles calculations for several representatives of high T
c compounds. In the single-layer cuprate HgBa2CuO4 the excess oxygen attracts electrons from the CuO2 plane leading to an increase of the hole concentration in this building block, where the maximum amount of holes is reached when the dopant oxygen shell is closed. The usage of supercells allows to study the inhomogeneous charge distribution as a function of doping, i.e. from the underdoped up to the overdoped regime. Comparison is made with other compounds like Ba-doped La2CuO4 and oxygen-deficient YBa2Cu3O7–x
. The effects of our findings on superconductivity are discussed. 相似文献
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Monodeep Chakraborty Jürgen Spitaler Peter Puschnig 《Computer Physics Communications》2010,181(5):913-920
We have developed an interface between the all-electron density functional theory code WIEN2k, and the MIT Ab-initio Phase Stability (MAPS) code of the Alloy-Theoretic Automated Toolkit (ATAT). WIEN2k is an implementation of the full-potential linearized augmented planewave method which yields highly accurate total energies and optimized geometries for any given structure. The ATAT package consists of two parts. The first one is the MAPS code, which constructs a cluster expansion (CE) in conjunction with a first-principles code. These results form the basis for the second part, which computes the thermodynamic properties of the alloy. The main task of the CE is to calculate the many-body potentials or effective cluster interactions (ECIs) from the first-principles total energies of different structures or supercells using the structure-inversion technique. By linking MAPS seamlessly with WIEN2k we have created a tool to obtain the ECIs for any lattice type of an alloy. We have chosen fcc Al-Ti and bcc W-Re to evaluate our implementation. Our calculated ECIs exhibit all features of a converged CE and compare well with literature results. 相似文献
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Analysis of electronic structure and charge density of the high-temperature superconductor YBa2Cu3O7
Self-consistent linearized augmented plane wave (LAPW) method calculations of the band structure, density of states, Fermi surface, Coulomb potential, charge density, core-level shifts, and electron-phonon interaction are presented for Y1Ba2Cu3O7. The calculated Sommerfield parameter is 4.35 mJ(mole Cu)–1 K–2, roughly about a factor of 2 smaller than experimentally deduced values of the enhanced value=(1 + )0, suggesting that the Fermi surface mass enhancement is of the order of unity. The crystal charge density is best represented by overlapping spherical ionic densities when the Cu and O ions are assigned charges of +1.62 and –1.69, respectively, corresponding to about 0.3 holes per oxygen atom. Core-level energies for the inequivalent atoms differ by as much as 0.45 eV for Cu and 0.7 eV for O, amounts which may be detectable by core-level spectroscopies. These results provide important information on the character and magnitude of ionic contributions to bonding in these materials. Within the rigid muffin-tin approximation, calculated McMillan-Hopfield parameters yield estimates for the electron-phonon strength that appear to be too small to account for the observedT
c. We point out an unusual band of oxygen-derived chain states below, but within 0.1 eV of, the Fermi level. 相似文献
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In the framework of density functional calculations and using the Linear Augmented Plane Waves with local orbital method (LAPW+lo), we have investigated the structural, electronic and optical properties of indium sulfoselenide (InS1−xSex). The present study confirms that InS1−xSex are indirect band gap materials. The non-linear dependence concentration x of the theoretical forbidden energy band is clearly visible and the microscopic origins of gap bowing are identified and calculated. In order to identify the angular momentum characteristics of the bands structure, the total and partial densities of states (DOS and PDOS) are analyzed. The feature bonding is also investigated from charge density study. Using the projected total densities of states (DOS) and the bands structure, we have calculated the linear optical properties, namely, the complex dielectric function ε(ω), refractive index n(ω), absorption coefficient α(ω) and the electron energy loss L(ω). In particular, we take into account the effect of Se composition on anisotropy, real part of the dielectric function and refractive index. The present alloy is found to be a challenging material in optoelectronic, medical and photovoltaic devices. Good agreements are found with the available experimental and theoretical results. 相似文献
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方向是通过密度泛函理论研究新材料的电子结构性质,对ZnO材料进行第一性原理研究,研究涉及的材料物性包括几何构型、电子结构特性等方面。所使用的是线性化缀加平面波方法的基本理论(LAPW),其中主要内容包括LAPW方法的简要理论和所使用的WIEN2K软件的介绍。具体的描述对ZnO材料的电子结构的计算与分析,并与半导体的典型结构特性相比较,得出结论。 相似文献
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