@article{schall_padgett_brenner_2005, title={Ad hoc continuum-atomistic thermostat for modeling heat flow in molecular dynamics simulations}, volume={31}, ISSN={["1029-0435"]}, DOI={10.1080/08927020512331336898}, abstractNote={An ad hoc thermostating procedure that couples a molecular dynamics (MD) simulation and a numerical solution to the continuum heat flow equation is presented. The method allows experimental thermal transport properties to be modeled without explicitly including electronic degrees of freedom in a MD simulation. The method is demonstrated using two examples, heat flow from a constant temperature silver surface into a single crystal bulk, and a tip sliding along a silver surface. For the former it is shown that frictional forces based on the Hoover thermostat applied locally to grid regions of the simulation are needed for effective feedback between the atomistic and continuum equations. For fast tip sliding the thermostat results in less surface heating, and higher frictional and normal forces compared to the same simulation without the thermostat.}, number={4}, journal={MOLECULAR SIMULATION}, author={Schall, JD and Padgett, CW and Brenner, DW}, year={2005}, month={Apr}, pages={283–288} }
 @article{areshkin_shenderova_schall_brenner_2005, title={Self-consistent tight binding model adapted for hydrocarbon systems}, volume={31}, ISSN={["1029-0435"]}, DOI={10.1080/08927020500044988}, abstractNote={A self-consistent environment-dependent tight binding method is presented that was developed to simulate eigenvalue spectra, electron densities and Coulomb potential distributions for hydrocarbon systems. The method builds on a non-self-consistent environment-dependent tight binding model for carbon [Tang et al., Phys. Rev. B 53, 979 (1996)] with parameters added to describe hydrocarbon bonds and to account for self-consistent charge transfer. A detailed description of the parameterization procedure is given. Case studies that examine electron emission-related properties of carbon nanotubes demonstrate the utility of the method. The results of these calculations indicate that field enhancement in the vicinity of a nanotube tip is higher for open-ended than for capped nanotubes. At the same time open-ended nanotubes exhibit a higher potential barrier in the tip region. This barrier deteriorates the coupling between conducting states in the nanotube and free electron states in vacuum, and may increase the field emission threshold.}, number={8}, journal={MOLECULAR SIMULATION}, author={Areshkin, DA and Shenderova, OA and Schall, JD and Brenner, DW}, year={2005}, month={Jul}, pages={585–595} }
 @article{areshkin_shenderova_schall_adiga_brenner_2004, title={A self-consistent tight binding model for hydrocarbon systems: application to quantum transport simulation}, volume={16}, ISSN={["1361-648X"]}, DOI={10.1088/0953-8984/16/39/018}, abstractNote={A self-consistent environment-dependent (SC-ED) tight binding (TB) method for hydrocarbons that was developed for quantum transport simulations is presented. The method builds on a non-self-consistent environment-dependent TB model for carbon (Tang et al 1996 Phys. Rev. B 53 979) with parameters added to describe hydrocarbon bonds and to account for self-consistent charge transfer. The SC-EDTB model assumes an orthogonal basis set. Orthogonality is a key element for adapting the SC-EDTB scheme to transport problems because it substantially increases the efficiency of the Newton–Raphson algorithm used to accelerate self-consistency convergence under non-equilibrium conditions. Compared to most existing TB schemes the SC-EDTB scheme is distinctive in two respects. First, self-consistency is added through the exact evaluation of Hartree and linear expansion of exchange integrals. All Hamiltonian elements belonging to the same atom are affected by charge transfer, not just the diagonal elements. The second distinction is the choice of SC-EDTB parameters; they were fitted to Mulliken populations and eigenvalue spectra rather than energies or elastic properties. The former are directly related to the conductivity and potential profile, which are essential for transport simulation. No two-centre repulsive term parametrization was performed. The functionality of the method is exemplified by computing I–V curves, non-equilibrium potential profiles and current density for a resonant tunnelling device.}, number={39}, journal={JOURNAL OF PHYSICS-CONDENSED MATTER}, author={Areshkin, DA and Shenderova, OA and Schall, JD and Adiga, SP and Brenner, DW}, year={2004}, month={Oct}, pages={6851–6866} }
 @article{schall_brenner_2004, title={Atomistic simulation of the influence of pre-existing stress on the interpretation of nanoindentation data}, volume={19}, ISSN={["0884-2914"]}, DOI={10.1557/JMR.2004.0410}, abstractNote={By using molecular dynamics simulations, we have accurately determined the true contact area during plastic indentation of materials under an applied in-plane stress. We found that the mean pressure calculated from the true contact area varied slightly with applied pre-stress with higher values in compression than in tension and that the modulus calculated from the true contact area is essentially independent of the press-stress level in the substrate. These findings are largely consistent with the findings of Tsui, Pharr, and Oliver. On the other hand, if the contact area is estimated from approximate formulae, the contact area is underestimated and shows a strong dependence on the pre-stress level. When it is used to determine mean pressure and modulus, the empirically determined area leads to large errors. Our simulations demonstrate that this phenomenon, first reported for macroscale hardness measurements dating back to 1932, also exists at the nanometer-scale contact areas, apparently scaling over 10 orders of magnitude in contact area, from ∼mm2 to ∼100 nm2.}, number={11}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Schall, JD and Brenner, DW}, year={2004}, month={Nov}, pages={3172–3180} }
 @article{areshkin_shenderova_schall_brenner_2003, title={Convergence acceleration scheme for self-consistent orthogonal-basis-set electronic structure methods}, volume={29}, ISSN={["1029-0435"]}, DOI={10.1080/0892702031000092197}, abstractNote={A new self-consistent convergence acceleration scheme that is a variant of the Newton-Raphson algorithm for non-linear systems of equations is presented. With this scheme, which is designed for use with minimal orthogonal basis set electronic structure methods, the conventional Newton-Raphson scaling with respect to the number of atoms is enhanced from quartic to cubic. The scheme is demonstrated using a self-consistent environment-dependent tight binding model for hydrocarbons that allows an efficient and reasonably precise simulation of charge density distortions due to external electric fields, finite system sizes, and surface effects. In the case of a metallic system, self-consistency convergence starts at a high fictitious temperature, typically 1500 K. As the electron density approaches the self-consistent configuration the temperature is decreased. Typically, seven to nine iterations are required to achieve self-consistency in metallic systems to a final temperature of 300 K. For systems with a finite band gap the convergence may start at the target temperature so that temperature reduction is unnecessary, and typically two iterations are needed to achieve self-consistency. The convergence algorithm can handle extremely high applied fields and is very robust with respect to initial electron densities.}, number={4}, journal={MOLECULAR SIMULATION}, author={Areshkin, DA and Shenderova, OA and Schall, JD and Brenner, DW}, year={2003}, month={Apr}, pages={269–286} }
 @article{brenner_shenderova_areshkin_schall_frankland_2002, title={Atomic modeling of carbon-based nanostructures as a tool for developing new materials and technologies}, volume={3}, number={5}, journal={Computer Modeling in Engineering & Sciences : CMES}, author={Brenner, D. W. and Shenderova, O. A. and Areshkin, D. A. and Schall, J. D. and Frankland, S. J. V.}, year={2002}, pages={643–673} }
 @article{schall_brenner_2000, title={Molecular dynamics simulations of carbon nanotube rolling and sliding on graphite}, volume={25}, ISSN={["0892-7022"]}, DOI={10.1080/08927020008044113}, abstractNote={Abstract Molecular dynamics simulations were carried out to investigate the origin of friction for carbon nanotubes on graphite substrates. In an initial simulation, a (10,10) nanotube was placed in an ‘in-registry’ starting position where the hexagonal lattice of the substrate matched that of the nanotube. In a second simulation, the substrate was oriented 90 degrees to the nanotube. A uniform force was applied to the nanotubes for 500 fs to set them into motion. The simulation was then run until the nanotubes stopped moving relative to the substrate. Only sliding was observed in the out-of-registry simulation, while periodic sliding and rolling was observed in the in-registry simulation. The latter is a result of the relatively larger surface corrugation for the in-registry case and occurs to avoid direct atomic collisions between nanotube and substrate atoms as the nanotube is moved along the substrate. Analysis of the kinetic energy suggests that the transition between sliding and rolling contributes to enhanced energy dissipation and higher net friction. These results are consistent with preliminary experimental observations by Superfine and coworkers.}, number={1-2}, journal={MOLECULAR SIMULATION}, author={Schall, JD and Brenner, DW}, year={2000}, pages={73–79} }
 @article{srivastava_brenner_schall_ausman_yu_ruoff_1999, title={Predictions of enhanced chemical reactivity at regions of local conformational strain on carbon nanotubes: Kinky chemistry}, volume={103}, ISSN={["1520-5207"]}, DOI={10.1021/jp990882s}, abstractNote={Simulations that model the effects of conformational strain on the chemical reactivity of single-walled carbon nanotubes suggest a method for significantly enhancing their reactivity locally by controlled deformations. The chemisorption of hydrogen atoms is predicted to be enhanced by as much as 1.6 eV at regions of high conformational deformation, suggesting that local reactivity will be significantly enhanced. Analysis of the local electronic density of states suggests the introduction of radical p orbital character to the sites that are locally deformed, consistent with the heightened reactivity and large pyramidalization angles at these sites. Preliminary experimental data consistent with this predicted heightened reactivity is also presented.}, number={21}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Srivastava, D and Brenner, DW and Schall, JD and Ausman, KD and Yu, MF and Ruoff, RS}, year={1999}, month={May}, pages={4330–4337} }