1,785 research outputs found
Characterization of Thin Film Materials using SCAN meta-GGA, an Accurate Nonempirical Density Functional
We discuss self-consistently obtained ground-state electronic properties of
monolayers of graphene and a number of beyond graphene compounds, including
films of transition-metal dichalcogenides (TMDs), using the recently proposed
strongly constrained and appropriately normed (SCAN) meta-generalized gradient
approximation (meta-GGA) to the density functional theory. The SCAN meta-GGA
results are compared with those based on the local density approximation (LDA)
as well as the generalized gradient approximation (GGA). As expected, the GGA
yields expanded lattices and softened bonds in relation to the LDA, but the
SCAN meta-GGA systematically improves the agreement with experiment. Our study
suggests the efficacy of the SCAN functional for accurate modeling of
electronic structures of layered materials in high-throughput calculations more
generally
Ab-initio Molecular Dynamics study of electronic and optical properties of silicon quantum wires: Orientational Effects
We analyze the influence of spatial orientation on the optical response of
hydrogenated silicon quantum wires. The results are relevant for the
interpretation of the optical properties of light emitting porous silicon. We
study (111)-oriented wires and compare the present results with those
previously obtained within the same theoretical framework for (001)-oriented
wires [F. Buda {\it et al.}, {\it Phys. Rev. Lett.} {\bf 69}, 1272, (1992)]. In
analogy with the (001)-oriented wires and at variance with crystalline bulk
silicon, we find that the (111)-oriented wires exhibit a direct gap at whose value is largely enhanced with respect to that found in bulk
silicon because of quantum confinement effects. The imaginary part of the
dielectric function, for the external field polarized in the direction of the
axis of the wires, shows features that, while being qualitatively similar to
those observed for the (001) wires, are not present in the bulk. The main
conclusion which emerges from the present study is that, if wires a few
nanometers large are present in the porous material, they are
optically active independently of their specific orientation.Comment: 14 pages (plus 6 figures), Revte
Spontaneous formation and stability of small GaP fullerenes
We report the spontaneous formation of a GaP fullerene cage in ab-initio
Molecular Dynamics simulations starting from a bulk fragment. A systematic
study of the geometric and electronic properties of neutral and ionized GaP
clusters suggests the stability of hetero-fullerenes formed by a compound with
zincblend bulk structure. We find that GaP fullerenes up to 28 atoms have high
symmetry, closed electronic shells, large HOMO-LUMO energy gaps and do not
dissociate when ionized. We compare our results for GaP with those obtained by
other groups for the corresponding BN clusters.Comment: To appear on PRL, 4 pages, 1 figure, Late
Domain wall tilting in the presence of the Dzyaloshinskii-Moriya interaction in out-of-plane magnetized magnetic nanotracks
We show that the Dzyaloshinskii-Moriya interaction (DMI) can lead to a
tilting of the domain wall (DW) surface in perpendicularly magnetized magnetic
nanotracks when DW dynamics is driven by an easy axis magnetic field or a spin
polarized current. The DW tilting affects the DW dynamics for large DMI and the
tilting relaxation time can be very large as it scales with the square of the
track width. The results are well explained by an analytical model based on a
Lagrangian approach where the DMI and the DW tilting are included. We propose a
simple way to estimate the DMI in a magnetic multilayers by measuring the
dependence of the DW tilt angle on a transverse static magnetic field. Our
results shed light on the current induced DW tilting observed recently in Co/Ni
multilayers with inversion asymmetry, and further support the presence of DMI
in these systems.Comment: 12 pages, 3 figures, 1 Supplementary Material
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Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25969/1/0000035.pd
Further search for a neutral boson with a mass around 9 MeV/c2
Two dedicated experiments on internal pair conversion (IPC) of isoscalar M1
transitions were carried out in order to test a 9 MeV/c2 X-boson scenario. In
the 7Li(p,e+e-)8Be reaction at 1.1 MeV proton energy to the predominantly T=0
level at 18.15 MeV, a significant deviation from IPC was observed at large pair
correlation angles. In the 11B(d,n e+e-)12C reaction at 1.6 MeV, leading to the
12.71 MeV 1+ level with pure T=0 character, an anomaly was observed at 9
MeV/c2. The compatibility of the results with the scenario is discussed.Comment: 12 pages, 5 figures, 2 table
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