15 research outputs found
Unrestricted Hartree-Fock theory of Wigner crystals
We demonstrate that unrestricted Hartree-Fock theory applied to electrons in
a uniform potential has stable Wigner crystal solutions for in
two dimensions and in three dimensions. The correlation energies
of the Wigner crystal phases are considerably smaller than those of the fluid
phases at the same density.Comment: 4 pages, 5 figure
Diffusion quantum Monte Carlo study of three-dimensional Wigner crystals
We report diffusion quantum Monte Carlo calculations of three-dimensional
Wigner crystals in the density range r_s=100-150. We have tested different
types of orbital for use in the approximate wave functions but none improve
upon the simple Gaussian form. The Gaussian exponents are optimized by directly
minimizing the diffusion quantum Monte Carlo energy. We have carefully
investigated and sought to minimize the potential biases in our Monte Carlo
results. We conclude that the uniform electron gas undergoes a transition from
a ferromagnetic fluid to a body-centered-cubic Wigner crystal at r_s=106+/-1.
The diffusion quantum Monte Carlo results are compared with those from
Hartree-Fock and Hartree theory in order to understand the role played by
exchange and correlation in Wigner crystals. We also study "floating" Wigner
crystals and give results for their pair-correlation functions
Analytic theory of ground-state properties of a three-dimensional electron gas at varying spin polarization
We present an analytic theory of the spin-resolved pair distribution
functions and the ground-state energy of an electron gas
with an arbitrary degree of spin polarization. We first use the Hohenberg-Kohn
variational principle and the von Weizs\"{a}cker-Herring ideal kinetic energy
functional to derive a zero-energy scattering Schr\"{o}dinger equation for
. The solution of this equation is implemented
within a Fermi-hypernetted-chain approximation which embodies the Hartree-Fock
limit and is shown to satisfy an important set of sum rules. We present
numerical results for the ground-state energy at selected values of the spin
polarization and for in both a paramagnetic and a fully
spin-polarized electron gas, in comparison with the available data from Quantum
Monte Carlo studies over a wide range of electron density.Comment: 13 pages, 8 figures, submitted to Phys. Rev.
Correlation energy of a two-dimensional electron gas from static and dynamic exchange-correlation kernels
We calculate the correlation energy of a two-dimensional homogeneous electron
gas using several available approximations for the exchange-correlation kernel
entering the linear dielectric response of the system.
As in the previous work of Lein {\it et al.} [Phys. Rev. B {\bf 67}, 13431
(2000)] on the three-dimensional electron gas, we give attention to the
relative roles of the wave number and frequency dependence of the kernel and
analyze the correlation energy in terms of contributions from the plane. We find that consistency of the kernel with the electron-pair
distribution function is important and in this case the nonlocality of the
kernel in time is of minor importance, as far as the correlation energy is
concerned. We also show that, and explain why, the popular Adiabatic Local
Density Approximation performs much better in the two-dimensional case than in
the three-dimensional one.Comment: 9 Pages, 4 Figure
From Homogenous to Heterogeneous: The Transformation of Beijing's Socio-Spatial Structure
Carboxymethylation of (1→6)-β-glucan (lasiodiplodan): Preparation, characterization and antioxidant evaluation
The Contribution of Dislocation Density and Velocity to the Strain Rate and Size Effect Using Transient Indentation Methods and Activation Volume Analysis
Charting the development of social and cultural geography in Mainland China: Voices from the inside
This article provides an overview of the recent development of social and cultural geography in China. It discusses six major bodies of work: cultural areas, cultural diffusion and cultural integration; geographies of ethnic cultures; cultural landscape and cultural economy; place and place-based cultural politics; marginal social groups; and geographies of social injustice. Although social and cultural geography is still located on the periphery of the disciplinary landscape of Chinese human geography, it is nonetheless developing into a noteworthy field of research. We start this review by calling attention to some problems in epistemologies and analytical approaches. Social and cultural geography in China often suffers from an analytical separation between environment and culture as ontologically enclosed entities. Also, it pays insufficient attention to the mutually constitutive relations between the social and the spatial. However, more recent studies have begun to engage with constructionist/poststructuralist approaches, and develop less positivist interpretations of space, social relations and cultural meanings. This review suggests that social and cultural geography in China needs to develop broader research scopes and strengthen theoretical frameworks. It concludes by calling for constructive dialogues between Chinese and Western human geographical scholarships. © 2014 © 2014 Taylor & Francis.Link_to_subscribed_fulltex