Structural stability, magnetic and electronic properties of Co2MnSi(001)/MgO heterostructures: A density functional theory study

A computational study of the epitaxial Co2MnSi(001)/MgO(001) interface relevant to tunneling magnetoresistive (TMR) devices is presented. Employing ab initio atomistic thermodynamics, we show that the Co- or MnSi-planes of bulk-terminated Co2MnSi form stable interfaces, while pure Si or pure Mn termination requires non-equilibrium conditions. Except for the pure Mn interface, the half-metallic property of bulk Co2MnSi is disrupted by interface bands. Even so, at homogeneous Mn or Co interfaces these bands contribute little to the minority-spin conductance through an MgO barrier, and hence such terminations could perform strongly in TMR devices.Comment: 4 pages, 3 fig

Quantum Monte Carlo calculations of H2_2 dissociation on Si(001)

We present quantum Monte Carlo calculations for various reaction pathways of H$_2$ with Si(001), using large model clusters of the surface. We obtain reaction energies and energy barriers noticeably higher than those from approximate exchange-correlation functionals. In improvement over previous studies, our adsorption barriers closely agree with experimental data. For desorption, the calculations give barriers for conventional pathways in excess of the presently accepted experimental value, and pinpoint the role of coverage effects and desorption from steps.Comment: 4 pages, 1 figur

Effect of post-growth annealing on the optical properties of InAs/GaAs quantum dots: A tight-binding study

We present an atomistic study of the strain field, the one-particle electronic spectrum and the oscillator strength of the fundamental optical transition in chemically disordered InxGa1−xAs pyramidal quantum dots (QDs). Interdiffusion across the interfaces of an originally “pure” InAs dot buried in a GaAs matrix is simulated through a simple model, leading to atomic configurations where the abrupt heterointerfaces are replaced by a spatially inhomogeneous composition profile x. Structural relaxation and the strain field calculations are performed through the Keating valence force field model, while the electronic and optical properties are determined within the empirical tight-binding approach. We analyze the relative impact of two different aspects of the chemical disorder, namely: (i) the effect of the strain relief inside the QD, and (ii) the purely chemical effect due to the group-III atomic species interdiffusion. We find that these effects may be quantitatively comparable, significantly affecting the electronic and optical properties of the dot. Our results are discussed in comparison with recent luminescence studies of intermixed QDs

Vitamin D binding protein and risk of renal cell carcinoma in the prostate, lung, colorectal and ovarian cancer screening trial

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155964/1/ijc32758.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155964/2/ijc32758_am.pd

Non-relativistic quantum systems on topological defects space-times

We study the behavior of non-relativistic quantum particles interacting with different potentials in the space-times generated by a cosmic string and a global monopole. We find the energy spectra in the presence of these topological defects and show how they differ from their free space-time values.Comment: 17 pages, LATEX fil

Highly site-specific H2 adsorption on vicinal Si(001) surfaces

Experimental and theoretical results for the dissociative adsorption of H_2 on vicinal Si(001) surfaces are presented. Using optical second-harmonic generation, sticking probabilities at the step sites are found to exceed those on the terraces by up to six orders of magnitude. Density functional theory calculations indicate the presence of direct adsorption pathways for monohydride formation but with a dramatically lowered barrier for step adsorption due to an efficient rehybridization of dangling orbitals.Comment: 5 pages, 4 figures, submitted to Phys. Rev. Lett. (1998). Other related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Influence of the substrate lattice structure on the formation of Quantum Well States in thin In and Pb films on silicon

The substrate lattice structure may have a considerable influence on the formation of quantum well states in a metal overlayer material. Here we study three model systems using angle resolved photoemission and low energy electron diffraction: indium films on Si(111) and indium and lead on Si(100). Data are compared with theoretical predictions based on density functional theory. We find that the interaction between the substrate and the overlayer strongly influences the formation of quantum well states; indium layers only exhibit well defined quantum well states when the layer relaxes from an initial face-centered cubic to the bulk body-centered tetragonal lattice structure. For Pb layers on Si(100) a change in growth orientation inhibits the formations of quantum well states in films thicker than 2 ML.Comment: 16 pages, 7 figure

Introducing and validating a single-item measure of identity leadership: The visual identity leadership scale (VILS)

In the present research, we introduce and validate a single-item measure of identity leadership—the visual identity leadership scale (VILS). The VILS uses Venn diagrams of sets of overlapping circles to denote different degrees of alignment between a leader's characteristics and behaviours and a group's values and goals. Key advantages of the VILS over other existing multi-item scales are that it provides a holistic assessment of identity leadership, is short, and can be adapted to address novel research questions that are impractical to address with existing scales (e.g. in diary studies, assessing multiple comparisons of many leaders or groups). Data from three studies (conducted in India, the United States and Germany) provide evidence of the VILS' construct reliability and validity. Results also showcase the instrument's capacity to be adapted to assess variations of identity leadership—for example, by assessing a leader's convergence with descriptive and ideal notions of collective self (i.e. with ‘who we are’ and ‘who we want to be’). We discuss the value of including the VILS in the toolbox that researchers and practitioners can utilize to expand our understanding of identity processes in leadership and group behaviour