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Using density functional theory, we investigate the structural, vibrational, and dielectric properties of titanium oxides and silicates, which have attracted considerable attention in the framework of the quest for alternative high-κ materials. For the oxides, three crystalline phases of titanium dioxide are considered. The first two are hypothetical; they are obtained by similarity with the cubic and tetragonal structure of zirconia ZrO2 or hafnia HfO2. The third is the rutile, a crystal that occurs naturally. For the silicates, we analyze a hypothetical TiSiO4 structure constructed by analogy with crystalline ZrSiO4 and HfSiO4 (zircon and hafnon). [ABSTRACT FROM AUTHOR]

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Presents calculations of the cohesive energy and bulk moduli of two hypothetical, negatively curved carbon networks. Finds that both have a cohesive energy smaller than that of graphite but significantly greater than that of C60. Stability of fullerenes; Euler's theorem; More.

The original article to which this Erratum refers was published in International Journal of Quantum Chemistry (2005) 101(6) 793– 801 [ABSTRACT FROM AUTHOR]

A scenario of metal cationization in which the organic molecule combines with a neutral excited metal atom is proposed. Ionization of the nascent complex occurs via ejection of an electron during the association process. Electron structure calculations for the model systems C6H6+Me (Me=Ag, Cu, Au) using the density functional theory give a strong argument in favor of the proposed mechanism. [Copyright &y& Elsevier]

The cationization of sputtered organic species via metal particle adduction is investigated using a series of molecules and metallic substrates. Analyte molecules include styrene-based oligomers with various molecular weights, poly(methyl methacrylate) and a polymer additive. The chosen substrates are Al, Cr, Cu, Pd, Ag, In, Au and Pb. Metal-cationization occurs for all the substrates except Al. The cationized molecule yields vary strongly with the considered molecule and substrate and they are not correlated with the metal ion yields. In addition, double cationization with two metal particles is observed in specific cases (Cu, Pd, Ag, and Au supports, styrene-based polymers with ∼13 repeat units or more). The combination of electronic structure calculations, molecular dynamics and Monte-Carlo simulations supports an emission scheme in which excited molecules and metal atoms recombine above the surface and decay via electron emission, thereby locking the complex in the ionic state. [Copyright &y& Elsevier]

The renormalization of electronic eigenenergies due to electron-phonon coupling (temperature dependence and zero-point motion effect) is sizable in many materials with light atoms. This effect, often neglected in ab initio calculations, can be computed using the perturbation-based Allen-Heine- Cardona theory in the adiabatic or non-adiabatic harmonic approximation. After a short description of the recent progresses in this field and a brief overview of the theory, we focus on the issue of phonon wavevector sampling convergence, until now poorly understood. Indeed, the renormalization is obtained numerically through a slowly converging q-point integration. For non-zero Born effective charges, we show that a divergence appears in the electron-phonon matrix elements at q G, leading to a divergence of the adiabatic renormalization at band extrema. This problem is exacerbated by the slow convergence of Born effective charges with electronic wavevector sampling, which leaves residual Born effective charges in ab initio calculations on materials that are physically devoid of such charges. Here, we propose a solution that improves this convergence. However, for materials where Born effective charges are physically non-zero, the divergence of the renormalization indicates a breakdown of the adiabatic harmonic approximation, which we assess here by switching to the non-adiabatic harmonic approximation. Also, we study the convergence behavior of the renormalization and develop reliable extrapolation schemes to obtain the converged results. Finally, the adiabatic and non-adiabatic theories, with corrections for the slow Born effective charge convergence problem (and the associated divergence) are applied to the study of five semiconductors and insulators: a-A1N, β-A1N, BN, diamond, and silicon. For these five materials, we present the zero-point renormalization, temperature dependence, phonon-induced lifetime broadening, and the renormalized electronic band structure. [ABSTRACT FROM AUTHOR]

Structural, electronic, vibrational, and dielectric properties of LaBGeO5 with the stillwellite structure are determined based on ab initio density functional theory. The theoretically relaxed structure is found to agree well with the existing experimental data with a deviation of less than 0.2%. Both the density of states and the electronic band structure are calculated, showing five distinct groups of valence bands. Furthermore, the Born effective charge, the dielectric permittivity tensors, and the vibrational frequencies at the center of the Brillouin zone are all obtained. Compared to existing model calculations, the vibrational frequencies are found in much better agreement with the published experimental infrared and Raman data, with absolute and relative1 firms values of 6.04 cm-1, and 1.81%, respectively. Consequently, numerical values for both the parallel and perpendicular components of the permittivity tensor are established as 3.55 and 3.71 (10.34 and 12.28), respectively, for the high-(low-)frequency limit. [ABSTRACT FROM AUTHOR]

The search for new materials based on computational screening relies on methods that accurately predict, in an automatic manner, total energy, atomic-scale geometries, and other fundamental characteristics of materials. Many technologically important material properties directly stem from the electronic structure of a material, but the usual workhorse for total energies, namely density-functional theory, is plagued by fundamental shortcomings and errors from approximate exchange-correlation functionals in its prediction of the electronic structure. At variance, the GW method is currently the state-of-the-art ab initio approach for accurate electronic structure. It is mostly used to perturbatively correct density-functional theory results, but is, however, computationally demanding and also requires expert knowledge to give accurate results. Accordingly, it is not presently used in high-throughput screening: fully automatized algorithms for setting up the calculations and determining convergence are lacking. In this paper, we develop such a method and, as a first application, use it to validate the accuracy of G0W0 using the PBE starting point and the Godby-Needs plasmon-pole model (G0W0GN@PBE) on a set of about 80 solids. The results of the automatic convergence study utilized provide valuable insights. Indeed, we find correlations between computational parameters that can be used to further improve the automatization of GW calculations. Moreover, we find that G0W0GN@PBE shows a correlation between the PBE and the G0W0GN@PBE gaps that is much stronger than that between GW and experimental gaps. However, the G0W0GN@PBE gaps still describe the experimental gaps more accurately than a linear model based on the PBE gaps. With this paper, we hence show that GW can be made automatic and is more accurate than using an empirical correction of the PBE gap, but that, for accurate predictive results for a broad class of materials, an improved starting point or some type of self-consistency is necessary. [ABSTRACT FROM AUTHOR]

The renormalization of the band structure at zero temperature due to electron-phonon coupling is explored in diamond, BN, LiF, and MgO crystals. We implement a dynamical scheme to compute the frequency-dependent self-energy and the resulting quasiparticle electronic structure. Our calculations reveal the presence of a satellite band below the Fermi level of LiF and MgO. We show that the renormalization factor (Z), which is neglected in the adiabatic approximation, can reduce the zero-point renormalization (ZPR) by as much as 40%. Anharmonic effects in the renormalized eigenvalues at finite atomic displacements are explored with the frozen-phonon method. We use a nonperturbative expression for the ZPR, going beyond the Allen-Heine-Cardona theory. Our results indicate that high-order electron-phonon coupling terms contribute significantly to the zero-point renormalization for certain materials. [ABSTRACT FROM AUTHOR]

The renormalization of electronic eigenenergies due to electron-phonon interactions (temperature dependence and zero-point motion effect) is important in many materials. We address it in the adiabatic harmonic approximation, based on first principles (e.g., density-functional theory), from different points of view: directly from atomic position fluctuations or, alternatively, from Janak's theorem generalized to the case where the Helmholtz free energy, including the vibrational entropy, is used. We prove their equivalence, based on the usual form of Janak's theorem and on the dynamical equation. We then also place the Allen-Heine-Cardona (AHC) theory of the renormalization in a first-principles context. The AHC theory relies on the rigid-ion approximation, and naturally leads to a self-energy (Fan) contribution and a Debye-Waller contribution. Such a splitting can also be done for the complete harmonic adiabatic expression, in which the rigid-ion approximation is not required. A numerical study within the density-functional perturbation theory framework allows us to compare the AHC theory with frozen-phonon calculations, with or without the rigid-ion approximation. For the two different numerical approaches without non-rigid-ion terms, the agreement is better than 7 μeV in the case of diamond, which represent an agreement tof ive significant digits. The magnitude of the non-rigid-ion terms in this case is also presented, distinguishing specific phonon modes contributions to different electronic eigenenergies. [ABSTRACT FROM AUTHOR]

We consider the effects of three different types of applied compressive stress on the structural, electronic and optical properties of rutile SnO 2 . We use standard density functional theory (DFT) to determine the structural parameters. The effective masses and the electronic band gap, as well as their stress derivatives, are computed within both DFT and many-body perturbation theory (MBPT). The stress derivatives for the SnO 2 direct band gap are determined to be 62, 38 and 25 meV/GPa within MBPT for applied hydrostatic, biaxial and uniaxial stress, respectively. Compared to DFT, this is a clear improvement with respect to available experimental data. We also estimate the exciton binding energies and their stress coefficients and compute the absorption spectrum by solving the Bethe–Salpeter equation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Theoretical non-linear susceptibility, electro-optic coefficients, Raman intensities. [•] Decomposition of the electro-optic tensor in phonon mode contributions. [•] Prediction of the frequencies of the silent phonon modes. [•] Detailed analysis of the Born effective charge tensor and its anisotropy. [•] Assessment of the predictive power of the theoretical formalism. [ABSTRACT FROM AUTHOR]