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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)

- Bei Peng, Mark Locascio, Peter Zapol, Shuyou Li, Steven L Mielke, George C Schatz +1 other
- Nature nanotechnology
- 2008

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)

- M Locascio, B Peng, P Zapol, Y Zhu, S Li, T Belytschko +1 other
- 2009

Recent studies have finally produced accurate measurements of the mechanical properties of carbon nanotubes, confirming the anticipated results computed from quantum and molecular mechanics. Several studies have also predicted an enhancement of these material properties as a result of electron irradiation. Here we prove conclusively through a rigorous TEM… (More)

- Zhenxing Feng, Lei Cheng, Chang-Yong Kim, Jeffrey W Elam, Zhan Zhang, Larry A Curtiss +2 others
- 2012

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 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)

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)

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)

The Shift-and-invert parallel spectral transformations (SIPs), a computational approach to solve sparse eigenvalue problems, is developed for massively parallel architectures with exceptional parallel scalability and robustness. The capabilities of SIPs are demonstrated by diagonalization of density-functional based tight-binding (DFTB) Hamiltonian and… (More)

Oxygen vacancies in proximity to surfaces and heterointerfaces in oxide thin film heterostructures have major effects on properties, resulting, for example, in emergent conduction behaviour, large changes in metal-insulator transition temperatures or enhanced catalytic activity. Here we report the discovery of a means of reversibly controlling the oxygen… (More)