Hasil untuk "Thermodynamics"

James H. Luscombe

We present three different neural network algorithms to calculate thermodynamic properties as well as dynamic correlation functions at finite temperatures for quantum lattice models. The first method is based on purification, which allows for the exact calculation of the operator trace. The second one is based on a sampling of the trace using minimally entangled states, whereas the third one makes use of quantum typicality. In the latter case, we approximate a typical infinite-temperature state by wave functions which are given by a product of a projected pair and a neural network part and evolve this typical state in imaginary time.

Jascha Narain Sohl-Dickstein, Eric A. Weiss, Niru Maheswaranathan et al.

A central problem in machine learning involves modeling complex data-sets using highly flexible families of probability distributions in which learning, sampling, inference, and evaluation are still analytically or computationally tractable. Here, we develop an approach that simultaneously achieves both flexibility and tractability. The essential idea, inspired by non-equilibrium statistical physics, is to systematically and slowly destroy structure in a data distribution through an iterative forward diffusion process. We then learn a reverse diffusion process that restores structure in data, yielding a highly flexible and tractable generative model of the data. This approach allows us to rapidly learn, sample from, and evaluate probabilities in deep generative models with thousands of layers or time steps, as well as to compute conditional and posterior probabilities under the learned model. We additionally release an open source reference implementation of the algorithm.

L. D'Alessio, Y. Kafri, A. Polkovnikov et al.

This review gives a pedagogical introduction to the eigenstate thermalization hypothesis (ETH), its basis, and its implications to statistical mechanics and thermodynamics. In the first part, ETH is introduced as a natural extension of ideas from quantum chaos and random matrix theory (RMT). To this end, we present a brief overview of classical and quantum chaos, as well as RMT and some of its most important predictions. The latter include the statistics of energy levels, eigenstate components, and matrix elements of observables. Building on these, we introduce the ETH and show that it allows one to describe thermalization in isolated chaotic systems without invoking the notion of an external bath. We examine numerical evidence of eigenstate thermalization from studies of many-body lattice systems. We also introduce the concept of a quench as a means of taking isolated systems out of equilibrium, and discuss results of numerical experiments on quantum quenches. The second part of the review explores the implications of quantum chaos and ETH to thermodynamics. Basic thermodynamic relations are derived, including the second law of thermodynamics, the fundamental thermodynamic relation, fluctuation theorems, the fluctuation–dissipation relation, and the Einstein and Onsager relations. In particular, it is shown that quantum chaos allows one to prove these relations for individual Hamiltonian eigenstates and thus extend them to arbitrary stationary statistical ensembles. In some cases, it is possible to extend their regimes of applicability beyond the standard thermal equilibrium domain. We then show how one can use these relations to obtain nontrivial universal energy distributions in continuously driven systems. At the end of the review, we briefly discuss the relaxation dynamics and description after relaxation of integrable quantum systems, for which ETH is violated. We present results from numerical experiments and analytical studies of quantum quenches at integrability. We introduce the concept of the generalized Gibbs ensemble and discuss its connection with ideas of prethermalization in weakly interacting systems.

U. Seifert

Stochastic thermodynamics as reviewed here systematically provides a framework for extending the notions of classical thermodynamics such as work, heat and entropy production to the level of individual trajectories of well-defined non-equilibrium ensembles. It applies whenever a non-equilibrium process is still coupled to one (or several) heat bath(s) of constant temperature. Paradigmatic systems are single colloidal particles in time-dependent laser traps, polymers in external flow, enzymes and molecular motors in single molecule assays, small biochemical networks and thermoelectric devices involving single electron transport. For such systems, a first-law like energy balance can be identified along fluctuating trajectories. For a basic Markovian dynamics implemented either on the continuum level with Langevin equations or on a discrete set of states as a master equation, thermodynamic consistency imposes a local-detailed balance constraint on noise and rates, respectively. Various integral and detailed fluctuation theorems, which are derived here in a unifying approach from one master theorem, constrain the probability distributions for work, heat and entropy production depending on the nature of the system and the choice of non-equilibrium conditions. For non-equilibrium steady states, particularly strong results hold like a generalized fluctuation–dissipation theorem involving entropy production. Ramifications and applications of these concepts include optimal driving between specified states in finite time, the role of measurement-based feedback processes and the relation between dissipation and irreversibility. Efficiency and, in particular, efficiency at maximum power can be discussed systematically beyond the linear response regime for two classes of molecular machines, isothermal ones such as molecular motors, and heat engines such as thermoelectric devices, using a common framework based on a cycle decomposition of entropy production.

Qun Luo, Yanling Guo, Bin Liu et al.

Abstract Magnesium and its alloys are significant superior metallic materials for structural components in automobile and aerospace industries due to their excellent physicomechanical properties. The Mg–rare earth (RE) systems have attracted great interests because RE additions can improve both the deformability and the strength of Mg alloys through solid solution strengthening and precipitation hardening mechanisms. This paper focuses on the interface stability, together with thermodynamics and kinetics of nucleation and growth of the key phases and matrix phases in Mg–RE alloys. In this paper, the theory and recent advances on Mg–RE alloys, especially for the interface stability, thermodynamics and kinetics of nucleation and growth of the key phases and matrix phases, together with their relationships with micro-structures, and macroscopic properties, are reviewed. By combining the thermodynamics/kinetics integrated simulations with various advanced experimental techniques, “reverse” design of Mg–RE alloys starting from the target service performance is put forward as a kind of scientific paradigm with rational design.

Shanhui Fan, Wei Li

Joshua A. Riback, Lian Zhu, M. Ferrolino et al.

H. Callen

Y. Çengel, M. Boles

S. D. Groot, P. Mazur

J. Rowlinson

M. Zuker, P. Stiegler

P. Ross, S. Subramanian

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Jr. John SantaLucia

A. Myers, J. Prausnitz

K. Pitzer

S. Dattagupta

A. Saggion, Rossella Faraldo, M. Pierno

Ruizheng Zhao, Xusheng Dong, P. Liang et al.

Poor thermodynamic stability and sluggish electrochemical kinetics of metallic Zn anode in aqueous solution greatly hamper its practical application. To solve such problems, to date, various zincophilic surface modification strategies are developed, which can facilitate reversible Zn plating/stripping behavior. However, there is still a lack of systematic and fundamental understanding regarding the metrics of thermodynamics inertia and kinetics zincophilia in selecting zincophilic sites. Herein, hetero‐metallic interfaces are prioritized for the first time via optimizing different hetero metals (Fe, Co, Ni, Sn, Bi, Cu, Zn, etc.) and synthetic solvents (ethanol, ethylene glycol, n‐propanol, etc.). Specifically, both theoretical simulations and experimental results suggest that this Bi@Zn interface can exhibit high efficiency owing to the thermodynamics inertia and kinetics zincophilia. A best practice for prioritizing zincophilic sites in a more practical metric is also proposed. As a proof of concept, the Bi@Zn anode delivers ultralow overpotential of ≈55 mV at a high rate of 10 mA cm−2 and stable cycle life over 4700 cycles. The elaborated “thermodynamics inertia and kinetics metalphilia” metrics for hetero‐metallic interfaces can benchmark the success of other metal‐based batteries.