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Electronic structure
About: Electronic structure is a research topic. Over the lifetime, 43996 publications have been published within this topic receiving 1163940 citations.
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TL;DR: In this paper, the electronic structure in solution theory developed in the preceding article is applied to the molecular ion I2−I+I− reaction system in the dipolar, aprotic solvent acetonitrile, which illustrates in detail the implementation of the general theory.
Abstract: The electronic structure in solution theory developed in the preceding article is applied to the molecular ion I2−■I+I− reaction system in the dipolar, aprotic solvent acetonitrile, which illustrates in detail the implementation of the general theory. A two‐dimensional, nonequilibrium free energy surface in the nuclear separation and a difference solvent coordinate is constructed via solution of a nonequilibrium solvation, nonlinear Schrodinger equation. The reduction to a single important solvent coordinate—from a manifold of three solvent coordinates—is motivated by an examination of the equilibrium solvation path and an analysis of the harmonic nonequilibrium fluctuations around this path. The evolving solute electronic structure over the basis of two orthogonal valence bond diabatic states—approximately corresponding to −II and II−—is discussed. Comparisons with the limiting Born–Oppenheimer and self‐consistent approximations for the solvent electronic polarization are made, with the former proving to...
27 citations
TL;DR: DFT-PAW calculations accurately reproduce changes in electron densities within nuclei in typical molecules, when PAW datasets constructed with finite nuclei are used, and are calibrated against all-electron, relativistic Dirac–Hartree–Fock, and coupled-cluster with single, double, and double excitation methods for estimating nuclear volume isotope effects.
Abstract: Mass-independent isotope fractionations driven by differences in volumes and shapes of nuclei (the field shift effect) are known in several elements and are likely to be found in more. All-electron relativistic electronic structure calculations can predict this effect but at present are computationally intensive and limited to modeling small gas phase molecules and clusters. Density functional theory, using the projector augmented wave method (DFT-PAW), has advantages in greater speed and compatibility with a three-dimensional periodic boundary condition while preserving information about the effects of chemistry on electron densities within nuclei. These electron density variations determine the volume component of the field shift effect. In this study, DFT-PAW calculations are calibrated against all-electron, relativistic Dirac–Hartree–Fock, and coupled-cluster with single, double (triple) excitation methods for estimating nuclear volume isotope effects. DFT-PAW calculations accurately reproduce changes in electron densities within nuclei in typical molecules, when PAW datasets constructed with finite nuclei are used. Nuclear volume contributions to vapor–crystal isotope fractionation are calculated for elemental cadmium and mercury, showing good agreement with experiments. The nuclear-volume component of mercury and cadmium isotope fractionations between atomic vapor and montroydite (HgO), cinnabar (HgS), calomel (Hg2Cl2), monteponite (CdO), and the CdS polymorphs hawleyite and greenockite are calculated, indicating preferential incorporation of neutron-rich isotopes in more oxidized, ionically bonded phases. Finally, field shift energies are related to Mossbauer isomer shifts, and equilibrium mass-independent fractionations for several tin-bearing crystals are calculated from 119Sn spectra. Isomer shift data should simplify calculations of mass-independent isotope fractionations in other elements with Mossbauer isotopes, such as platinum and uranium.
27 citations
TL;DR: In this article, the structural, anisotropic elastic and electronic properties of binary intermetallic compounds using first-principles plane-wave pseudo-potential method were studied.
27 citations
TL;DR: In this paper, the band structure of ternary alloys, which are easier to grow than binary Ge 1-x Sn x alloys and offer a wider tunability of their direct band-gap and other properties, was calculated and investigated by using the empirical pseudo-potential plane wave method with modified Falicov pseudo potential form function.
Abstract: The band structure of Ge 1 − x − y Si x Sn y ternary alloys, which are easier to grow than binary Ge 1-x Sn x alloys, and clearly offer a wider tunability of their direct band-gap and other properties, was calculated and investigated by using the empirical pseudo-potential plane wave method with modified Falicov pseudo-potential formfunction. The virtual crystal approximation (VCA) and 2 × 2 × 2 super-cell (mixed atoms) method were adopted to model the alloy. In order to calculate all of these properties, the empirical pseudo-potential code was developed. The lattice constant of the alloy varies between 0.543 to 0.649 nm. The regions in the parameter space that corresponds to a direct or indirect band gap semiconductor are identified. The Ge 1 − x − y Si x Sn y ternary alloy shows the direct band gap for appropriate composition of Si, Ge and Sn. The direct energy gap is in the range 0–1.4 eV (from the VCA calculation), and 0–0.8 eV (from the super-cell calculation), depending on the alloy composition. Therefore, this alloy is a promising material for optoelectronic applications in both visible and infrared range, such as interband lasers or, solar cells. Furthermore, strain-free heterostructures based on such alloys are designed and, using the effective-mass Hamiltonian model, the electronic structure of GeSiSn quantum wells with arbitrary composition is investigated, in order to understand their properties and the potential of their use in devices.
27 citations
TL;DR: In this article, a theoretical study of ordering in Fe-Al alloys assuming different underlying magnetic structures: paramagnetic, ferromagnetic, and disordered local moments (DLM's).
Abstract: We present a theoretical study of ordering in Fe-Al alloys assuming different underlying magnetic structures: paramagnetic, ferromagnetic, and disordered local moments (DLM's). We calculate the effective pair (chemical) interactions using the generalized perturbation method (GPM) in the linear muffin tin orbital basis. The reference medium for the GPM is chosen as the completely disordered state of the alloy, with its electronic structure described via the coherent potential approximation. The effective pair interactions are used to obtain the ordered superlattice structures and to estimate the order-disorder transition temperatures. The tendency of primary ordering to the B2 structure and secondary ordering to the ${\mathrm{DO}}_{3}$ structure is examined as a function of Fe concentration. We find that the tendency to B2 (CsCl) ordering decreases in sequence from the paramagnetic to the DLM's and to the ferromagnetic model. The tendency to secondary ordering in the ${\mathrm{DO}}_{3}$ structure is strongest in the ferromagnetic model and is found to increase with Fe concentration due to enhanced spin polarization. Factors such as lattice relaxation, charge transfer, and alloy volume (per atom) are found to be much more important for secondary than for primary ordering. Although the model provides a way to study the ordering tendency in the alloy based on an ab initio electronic structure calculation, it is deficient in capturing all the intricacies of the interplay between magnetic and chemical structure. Effects of spin fluctuations on the order-disorder transition are also neglected.
27 citations