@article{pomorski_pastewka_roland_guo_wang_2004, title={Capacitance, induced charges, and bound states of biased carbon nanotube systems}, volume={69}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.69.115418}, abstractNote={Although it has long been known that the classical notions of capacitance need modification at the nanoscale, in order to account for important quantum effects, very few first-principles investigations of these properties exist for any real material systems. Here we present the results of a large-scale ab initio investigation of the capacitance properties of carbon nanotube systems. The simulations are based on a recently developed real-space nonequilibrium Green's-function approach, with special attention being paid to the treatment of the bound states present in the system. In addition, use has been made of a symmetry decomposition scheme for the charge density. This is needed both to speed up the calculations and in order to study the origins of the induced charges. Specific systems investigated include two and three nested nanotube shells, the insertion of a capped nanotube into another, a connected (12,0)/(6,6) nanotube junction, and the properties of a nanotube acting as a probe over a flat aluminum surface. First-principles estimates of the capacitance matrix coefficients for all these systems are provided, along with a discussion of the quantum corrections. For the case of the nanotube junction, the numerical value of the capacitance is sufficiently high, as to be useful for future device applications.}, number={11}, journal={PHYSICAL REVIEW B}, author={Pomorski, P and Pastewka, L and Roland, C and Guo, H and Wang, J}, year={2004}, month={Mar} }
 @article{pomorski_roland_guo_wang_2003, title={First-principles investigation of carbon nanotube capacitance}, volume={67}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.67.161404}, abstractNote={With ab initio simulations based on a real-space nonequilibrium Green's function formalism, we have investigated the charging of carbon nanotube systems. The charging effects are described by capacitance coefficients, for which we provide a first-principles estimate. Specifically, the capacitance matrix of nested armchair nanotubes, the insertion of one nanotube into another, and a junction of two metallic nanotubes with a large conductance gap were calculated with a focus on investigating the bias-induced charges. For the case of the nanotube junction, the numerical value of the capacitance is sufficiently high, as to be useful for future device applications.}, number={16}, journal={PHYSICAL REVIEW B}, author={Pomorski, P and Roland, C and Guo, H and Wang, J}, year={2003}, month={Apr} }
 @article{powell_wang_aspnes_2002, title={Simplified bond-hyperpolarizability model of second harmonic generation}, volume={65}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.65.205320}, abstractNote={We show that the anisotropies of second-harmonic-generation (SHG) intensities of vicinal (111) and (001)Si-SiO 2 interfaces can he described accurately as dipole radiation originating from the anharmonic motion of band charges strictly along bond directions. This simplified bond-hyperpolarizability model not only substantially simplifies the description of SHG, but also provides a microscopically physical and mathematically more efficient picture of the process than those found in standard phenomenological treatments employing tensor or Fourier coefficients. Using this approach we obtain an analytic solution for the expected response of (111) terraces, and by comparing to data show that the effective angles of incidence and observation for the (111)Si-SiO 2 interface are not those measured in the laboratory hut correspond to those refracted at the air-SiO 2 interface. For (111) vicinal interfaces at 765 nm SHG absorption is found to occur mainly for the step bond. The success of this formulation indicates that in many, if not most, cases the description of SHG may be simpler than that of the linear-optical response.}, number={20}, journal={PHYSICAL REVIEW B}, author={Powell, GD and Wang, JF and Aspnes, DE}, year={2002}, month={May} }
 @article{wang_powell_johnson_lucovsky_aspnes_2002, title={Simplified bond-hyperpolarizability model of second harmonic generation: Application to Si-dielectric interfaces}, volume={20}, ISSN={["2166-2746"]}, DOI={10.1116/1.1493783}, abstractNote={We show that the anisotropies of second-harmonic-generation (SHG) intensities of singular and vicinal (111) and (001)Si–dielectric interfaces can be described accurately as dipole radiation originating from the anharmonic motion of bond charges parallel to the bond directions. This simplified bond-hyperpolarizability model not only provides a simpler and mathematically more efficient representation of SHG, but also allows a direct physical interpretation at the bond level, which was lacking in previous approaches. Application to oxidized and nitrided Si–SiO2 interfaces provides new insight into bonding that occurs at these interfaces as well as the origin of SHG.}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Wang, JFT and Powell, GD and Johnson, RS and Lucovsky, G and Aspnes, DE}, year={2002}, pages={1699–1705} }