Theory of Dense Hydrogen and Correlated Quantum and Classical Systems

稠密氢理论及相关量子和经典系统

基本信息

  • 批准号:
    9988576
  • 负责人:
  • 金额:
    --
  • 依托单位:
  • 依托单位国家:
    美国
  • 项目类别:
    Continuing grant
  • 财政年份:
    2000
  • 资助国家:
    美国
  • 起止时间:
    2000-03-01 至 2003-02-28
  • 项目状态:
    已结题

项目摘要

9988576AshcroftThe grant supports theoretical studies of dense hydrogen (extended to certain light elements), and of correlated quantum and classical systems with novel states of order. In one sense hydrogen, the most abundant of elements (and rife in its combination with others) can be regarded at high compression as the simplest realistic and quantifiable departure from the ubiquitous jellium. It is a fundamental system and, given the simplicity of its basic Hamiltonian, its properties in the condensed phase are intriguingly complex. Hydrogen has recently come under very sustained experimental attack both dynamically and statically. Laser shock experiments now take hydrogen into a regime of around ten-fold compression (over the one atmosphere solid) and temperatures as high as 20,000K. Yet there seems to be little in the way of theoretical consensus on accounting even for something so basic as the equation of state under these conditions.The first of three major research themes, on dense hydrogen, is prompted by the fact that both at high temperatures and at low there is a remarkable persistence of proton-pairing: for near the ground state conditions this has been shown to be accompanied by unusual states of electronic order, the extent and range of which invite further investigation. At very high temperatures it is reasonably expected that the pairing will give way to a dense monatomic and metallic state, but en route we are presented with intermediate conditions (partially degenerate electrons, and especially strong pairing correlations in the protons) that give rise to a problem of considerable complexity. There will be a range of transitions on the way to the upper reaches of the phase diagram, and whether some of these are continuous or not is already a matter of debate. It is known experimentally that the low temperature/high density phase diagram of hydrogen (and deuterium) is rich, and yet it has received only partial explanation in terms of the ordering of quadrupoles. One interesting challenge is to incorporate the new physics associated with the experimental observation of electronic broken symmetry leading to self-consistent fields of a largely dipolar character to which the quadrupolar problem can now couple.A second major effort is to be centered on many-body theory, following on the heels of a prediction that at high densities the light s-p metals may have electronic structures unusually different from their one atmosphere counterparts. This arises from a generalized view of pairing in Coulomb systems (but extended to the case of pseudopotentials) and leads to the possibility of new ordered states in systems hitherto regarded as relatively simple. The generalized pairing view itself can also now be extended to anisotropic systems, those of most immediate interest being layered. The nature of effective interactions in such systems, particularly if the one-electron structure admits of a particle-hole character, is of considerable interest. For then the interactions can depart significantly from the corresponding results in three dimensions. In the quasi-two-dimensional electron gas the issue is also of some interest with respect to the possibility of intrinsic superconductivity (i.e. that the true ground state of quasi-two-dimensional electron-hole ensembles might exhibit off-diagonal long range order). When such systems are taken to quite low densities, symmetry breaking to a crystalline state is anticipated, though as in three-dimensions it appears now that the standard constraint (to simple Bravais lattices) does not necessarily lead to states of lowest energy. The third theme deals with density functional theory which has also had wide applications in a classical context, and in particular has had a major impact on the theory of classical inhomogeneous systems. Classical systems are often more highly correlated than their quantum analogs, and for this reason the class of approximations developed here (coarse graining and weighted density methods, for example) might well find application now in electronic systems. The new studies may therefore be viewed as an exploration of a possible alternative to gradient correction approaches to the ubiquitous local density or local spin density approximation.%%% This grant supports theoretical research on condensed matter systems. There are three broad themes: the study of the simplest element, hydrogen, and its behavior at high pressures and temperature; the study of interacting charged quantum particles; and, the study of classical interacting systems. The research ranges from very basic investigations of the foundations of the physics of interacting systems to realistic calculations of novel new phases of hydrogen.***
9988576阿什克罗夫特这笔赠款支持对稠密氢(扩展到某些轻元素)以及具有新颖有序态的相关量子和经典系统的理论研究。 从某种意义上说,氢这种最丰富的元素(并且在与其他元素的组合中非常丰富)在高压缩下可以被视为与无处不在的水母最简单的现实和可量化的背离。 它是一个基本系统,鉴于其基本哈密顿量的简单性,其在凝聚相中的性质非常复杂。 氢最近在动态和静态方面都受到了非常持续的实验攻击。 激光冲击实验现在将氢置于大约十倍压缩的状态(在一个大气压的固体上)和高达 20,000K 的温度。 然而,即使是在这些条件下解释像状态方程这样基本的东西,在理论上也几乎没有达成共识。三个主要研究主题中的第一个是关于稠密氢,其原因是在高温和低温下质子配对都显着持续存在:对于接近基态的条件,这已被证明伴随着不寻常的电子秩序状态,其程度和范围需要进一步研究。 在非常高的温度下,可以合理地预期配对将让位于致密的单原子和金属态,但在途中我们遇到了中间条件(部分简并电子,尤其是质子中强烈的配对相关性),这引起了相当复杂的问题。 在到达相图上游的过程中将会出现一系列的转变,其中一些转变是否连续已经是一个争论的问题。 通过实验已知氢(和氘)的低温/高密度相图丰富,但在四极有序方面仅得到部分解释。 一个有趣的挑战是整合与电子破缺对称性实验观察相关的新物理学,从而产生具有很大程度上偶极特征的自洽场,四极问题现在可以耦合到该场。第二个主要努力是集中在多体理论上,紧随其后的预测是,在高密度下,轻的 s-p 金属可能具有与它们在大气层中的对应物不同寻常的电子结构。 这源于库仑系统配对的广义观点(但扩展到赝势的情况),并导致迄今为止被认为相对简单的系统中新的有序状态的可能性。 广义配对视图本身现在也可以扩展到各向异性系统,那些最直接感兴趣的系统是分层的。 这种系统中有效相互作用的本质,特别是当单电子结构具有粒子-空穴特征时,引起了人们的极大兴趣。 因此,相互作用可能会与三个维度上的相应结果显着背离。 在准二维电子气中,关于本征超导性的可能性(即准二维电子空穴系综的真实基态可能表现出非对角长程有序)的问题也很有趣。 当这样的系统达到相当低的密度时,预计对称性会破缺到结晶态,尽管在三维中,现在看来标准约束(对于简单的布拉维晶格)并不一定会导致最低能量的状态。 第三个主题涉及密度泛函理论,该理论在经典背景下也有广泛的应用,特别是对经典非齐次系统理论产生了重大影响。 经典系统通常比它们的量子类似物具有更高的相关性,因此,这里开发的近似类(例如粗粒度和加权密度方法)现在很可能在电子系统中找到应用。 因此,新研究可以被视为对普遍存在的局域密度或局域自旋密度近似的梯度校正方法的可能替代方案的探索。%%% 这项资助支持凝聚态物质系统的理论研究。 共有三大主题:研究最简单的元素氢及其在高压和高温下的行为;带电量子粒子相互作用的研究;以及经典相互作用系统的研究。 研究范围从相互作用系统的物理基础的非常基础的研究到氢的新相的实际计算。***

项目成果

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Neil Ashcroft其他文献

Neil Ashcroft的其他文献

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{{ truncateString('Neil Ashcroft', 18)}}的其他基金

Superconductivity and Other Quantum Orderings in the Lighter Elements
轻元素中的超导性和其他量子有序性
  • 批准号:
    0907425
  • 财政年份:
    2009
  • 资助金额:
    --
  • 项目类别:
    Standard Grant
Orderings in Highly Quantal Light Element Systems
高量子轻元件系统的订单
  • 批准号:
    0601461
  • 财政年份:
    2006
  • 资助金额:
    --
  • 项目类别:
    Continuing Grant
Correlated Quantum and Classical Systems; Dense Light Elements and Their Combinations
相关的量子和经典系统;
  • 批准号:
    0302347
  • 财政年份:
    2003
  • 资助金额:
    --
  • 项目类别:
    Continuing Grant
REU SITE: REU Site Program for Interdisciplinary Materials Studies at the Cornell Center for Materials Research
REU 站点:康奈尔材料研究中心跨学科材料研究 REU 站点项目
  • 批准号:
    9820543
  • 财政年份:
    1999
  • 资助金额:
    --
  • 项目类别:
    Continuing grant
Theory of Dense Hydrogen and Correlated Quantum and Classical Systems
稠密氢理论及相关量子和经典系统
  • 批准号:
    9619854
  • 财政年份:
    1997
  • 资助金额:
    --
  • 项目类别:
    Continuing grant
MRSEC: Materials Science and Engineering Research Center
MRSEC:材料科学与工程研究中心
  • 批准号:
    9632275
  • 财政年份:
    1996
  • 资助金额:
    --
  • 项目类别:
    Cooperative Agreement
Fluctuation, Correlation, and Order in Dense Quantum and Classical Systems
稠密量子和经典系统中的涨落、相关性和秩序
  • 批准号:
    9319864
  • 财政年份:
    1994
  • 资助金额:
    --
  • 项目类别:
    Continuing grant
Fluctuations and Order: Theories of Correlated Electronic- and Classical-Systems
波动与秩序:相关电子系统和经典系统的理论
  • 批准号:
    9017281
  • 财政年份:
    1991
  • 资助金额:
    --
  • 项目类别:
    Continuing grant
Fluctuations and Order: Theory of Highly Correlated Electronic and Classical Systems
涨落与秩序:高度相关的电子与经典系统理论
  • 批准号:
    8715590
  • 财政年份:
    1987
  • 资助金额:
    --
  • 项目类别:
    Continuing grant
Microscopic Theory of Disordered Systems: Non-Simple Fluidsand Glasses; U.S.-Italy Program
无序系统的微观理论:非简单流体和玻璃;
  • 批准号:
    8514849
  • 财政年份:
    1986
  • 资助金额:
    --
  • 项目类别:
    Standard Grant

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