arXiv subjects

Daniel Neuhauser

Publications and source records attributed to Daniel Neuhauser.

60 records · Page 4Linked to original sources

arXiv2012

Expeditious Stochastic Calculation of Random-Phase Approximation Energies for Thousands of Electrons in 3 Dimensions

A fast method is developed for calculating the Random-Phase-Approximation (RPA) correlation energy for density functional theory. The correlation energy is given by a trace over a projected RPA response matrix and the trace is taken by a stochastic approach using random perturbation vectors. The method scales, at most, quadratically with the system size but in practice, due to self-averaging, requires less statistical sampling as the system grows and the performance is close to linear scaling. We demonstrate the method by calculating the RPA correlation energy for cadmium selenide and silicon nanocrystals with over 1500 electrons. In contrast to 2nd order Møller-Plesset correlation energies, we find that the RPA correlation energies per electron are largely independent on the nanocrystal size.

physics.chem-ph↗

arXiv2012

Expeditious stochastic approach for MP2 energies in large electronic systems

A fast stochastic method for calculating the 2nd order Møller-Plesset (MP2) correction to the correlation energy of large systems of electrons is presented. The approach is based on reducing the exact summation over occupied and unoccupied states to a time-dependent trace formula amenable to stochastic sampling. We demonstrate the abilities of the method to treat systems of thousands electrons using hydrogen passivated silicon spherical nanocrystals represented on a real space grids, much beyond capabilities of present day MP2 implementations.

physics.chem-ph↗

arXiv2007

Hydrodynamic Tensor-DFT with correct susceptibility

In a previous work we developed a family of orbital-free tensor equations for DFT [J. Chem. Phys. 124, 024105 (2006)]. The theory is a combination of the coupled hydrodynamic moment equations hierarchy with a cumulant truncation of the one-body electron density matrix. A basic ingredient in the theory is how to truncate the series of equation of motion for the moments. In the original work we assumed that the cumulants vanish above a certain order (N). Here we show how to modify this assumption to obtain the correct susceptibilities. This is done for N=3, a level above the previous study. At the desired truncation level a few relevant terms are added, which, with the right combination of coefficients, lead to excellent agreement with the Kohn-Sham Lindhard susceptibilities for an uninteracting system. The approach is also powerful away from linear response, as demonstrated in a non-perturbative study of a jellium with a repulsive core, where excellent matching with Kohn-Sham simulations is obtained while the Thomas Fermi and von-Weiszacker methods show significant deviations. In addition, time-dependent linear response studies at the new N=3 level demonstrate our previous assertion that as the order of the theory is increased, new additional transverse sound modes appear mimicking the RPA transverse dispersion region.

cond-mat.mtrl-sci↗

arXiv2005

Bogoliubov-like mode in the Tonks-Girardeau Gas

We reformulate 1D boson-fermion duality in path-integral terms. The result is a 1D counterpart of the boson-fermion duality in the 2D Chern-Simons gauge theory. The theory is consistent and enables, using standard resummation techniques, to obtain the long-wave-length asymptotics of the collective mode in 1D boson systems at the Tonks-Girardeau regime. The collective mode has the dispersion of Bogoliubov phonons: $ω(q)=q \sqrt{\barρU(q)/m}$, where $\barρ$ is the bosons density and $U(q)$ is a Fourier component of the two-body potential.

cond-mat.str-el↗

arXiv2004

A density functional theory with correct long-range asymptotic behavior

We derive an exact representation of the exchange-correlation energy within density functional theory (DFT) which spawns a class of approximations leading to correct long-range asymptotic behavior. In what amounts to be the simplest approximation, we obtain an electronic structure theory that combines a new local correlation en-ergy (based on Monte-Carlo calculations applied to the homogeneous electron gas (HEG)) and a combination of local and explicit long-ranged exchange. The theory is applied to several 1st row atoms and diatomic molecules where encouraging results are obtained: a good description of the chemical bond at the same time allowing for bound anions, reasonably accurate affinity energies and correct polarizability of an elongated hydrogen chain. Further stringent tests of DFT are passed: the ratio of ionization potential and highest orbital energy is close to unity and the atomic charge of two distant hydrogen atoms under large bias is quantized (integer).

cond-mat.mtrl-sci↗

arXiv2004

A Liouville equation for systems which exchange particles with reservoirs: transport through a nano-device

A Redfield-like Liouville equation for an open system that couples to one or more leads and exchanges particles with them is derived. The equation is presented for a general case. A case study of time-dependent transport through a single quantum level for varying electrostatic and chemical potentials in the leads is presented. For the case of varying electrostatic potentials the proposed equation yields, for the model study, the results of an exact solution.

physics.chem-ph↗