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SIPs is a new efficient and robust software package implementing multiple shift-and-invert spectral transformations on parallel computers. Built on top of SLEPc and PETSc, it can compute very large numbers of eigenpairs for sparse symmetric generalized eigenvalue problems. The development of SIPs is motivated by applications in nanoscale materials modeling,(More)
The excellent mechanical properties of carbon nanotubes are being exploited in a growing number of applications from ballistic armour to nanoelectronics. However, measurements of these properties have not achieved the values predicted by theory due to a combination of artifacts introduced during sample preparation and inadequate measurements. Here we report(More)
A framework is proposed for the investigation of chemical and mechanical properties of nanostructures. The methodology is based on a two-step approach to compute the electronic density distribution in and around a nanostructure, and then the equilibrium configuration of its nuclei. The Electronic Problem embeds interpolation and coupled cross-domain(More)
Atomic-scale study of ambient-pressure redox-induced changes for an oxide-supported sub-monolayer catalyst: VO X / α-TiO 2 (110) I. Primitive unit cell and (110) surface unit cell of α α α α-TiO 2 For convenience of working with the α-TiO 2 (110) surface, a non-primitive tetragonal surface unit cell is defined. Figure S1 shows the conventional primitive(More)
Density functional theory (DFT) can accurately predict chemical and mechanical properties of nanostruc-tures, although at a high computational cost. A quasicontinuum-like framework is proposed to substantially increase the size of the nanostructures that can be simulated ab initio. This increase stems from two facts. First, in order to find approximate(More)
Density functional theory can accurately predict chemical and mechanical properties of nanostructures, although at a high computational cost. A quasicontinuum-like framework is proposed to substantially increase the size of the nanostructures accessible to simulation. It takes advantage of the near periodicity of the atomic positions in some regions of(More)
The paper investigates model reduction techniques that are based on a nonlocal quasi-continuum-like approach. These techniques reduce a large optimization problem to either a system of nonlinear equations or another optimization problem that are expressed in a smaller number of degrees of freedom. The reduction is based on the observation that many of the(More)
A set of interatomic pair potentials were derived for gallium nitride within the shell-model approach. It was shown that the potential set successfully reproduces the properties of the fourfold-coordinated wurtzite and zinc-blende structures as well as the sixfold-coordinated rock-salt structure. The high-pressure phase transition from wurtzite to rock-salt(More)
Fluorescence intermittency or blinking is observed in nearly all nanoscale fluorophores. It is characterized by universal power-law distributions in on- and off-times as well as 1/f behaviour in corresponding emission power spectral densities. Blinking, previously seen in confined zero- and one-dimensional systems has recently been documented in(More)