NONISOTHERMAL METASTABILITY IN MESOSCOPIC SYSTEMS

1991 ◽  
Vol 05 (06) ◽  
pp. 447-453 ◽  
Author(s):  
H. DEKKER
Keyword(s):  
Heat Capacity ◽  
Free Energy ◽  
Heat Exchange ◽  
Energy Barrier ◽  
Degrees Of Freedom ◽  
Helmholtz Free Energy ◽  
Nonequilibrium Thermodynamics ◽  
Magnetic Phase ◽  
Planck Equation ◽  
Temperature Dependent

Since the effective potential for noisy “macroscopic” degrees of freedom (e.g. the magnetic phase in Josephson junctions) in general depends on the (local) temperature, it is given thermodynamical significance as the Gibbs or Helmholtz free energy. Using the notions of nonequilibrium thermodynamics a generalized Kramers Fokker-Planck equation is then presented, which includes nonisothermal effects. The escape rate from a metastable state across a temperature-dependent energy barrier is investigated. A substantial entropic barrier enhancement is found for a specimen with small heat capacity and slow heat exchange with its environment (e.g. the helium reservoir).

scholarly journals Free Energy of Metals from Quasi-Harmonic Models of Thermal Disorder

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 195
Author(s):  
Pavel A. Korzhavyi ◽  
Jing Zhang
Keyword(s):  
Free Energy ◽  
First Principles ◽  
Density Functional ◽  
Helmholtz Free Energy ◽  
Complex Materials ◽  
Predictive Capability ◽  
Temperature Dependent ◽  
Disordered Alloys ◽  
Thermal Disorder ◽  
Structure Calculations

A simple modeling method to extend first-principles electronic structure calculations to finite temperatures is presented. The method is applicable to crystalline solids exhibiting complex thermal disorder and employs quasi-harmonic models to represent the vibrational and magnetic free energy contributions. The main outcome is the Helmholtz free energy, calculated as a function of volume and temperature, from which the other related thermophysical properties (such as temperature-dependent lattice and elastic constants) can be derived. Our test calculations for Fe, Ni, Ti, and W metals in the paramagnetic state at temperatures of up to 1600 K show that the predictive capability of the quasi-harmonic modeling approach is mainly limited by the electron density functional approximation used and, in the second place, by the neglect of higher-order anharmonic effects. The developed methodology is equally applicable to disordered alloys and ordered compounds and can therefore be useful in modeling realistically complex materials.

Dyonic and Magnetic Black Holes with Rational Nonlinear Electrodynamics

2020 ◽  
Author(s):  
Sergey Kruglov
Keyword(s):  
Black Holes ◽  
Heat Capacity ◽  
Black Hole ◽  
Free Energy ◽  
Phase Transitions ◽  
Helmholtz Free Energy ◽  
Magnetic Charge ◽  
The Self ◽  
Nonlinear Electrodynamics ◽  
Dual Case

The principles of causality and unitarity are studied within rational nonlinear electrodynamics proposed earlier. We investigate dyonic and magnetized black holes and show that in the self-dual case, when the electric charge equals the magnetic charge, corrections to Coulomb's law and Reissner-Nordstrom solutions are absent. In the case of the magnetic black hole, the Hawking temperature, the heat capacity and the Helmholtz free energy are calculated. It is shown that there are second-order phase transitions and it was demonstrated that at some range of parameters the black holes are stable.

Thermoelastic Generalization of Isothermal Elastic Constitutive Models for Rubber-Like Materials

1996 ◽  
Vol 69 (2) ◽  
pp. 313-324 ◽  
Author(s):  
Nianning Zeng ◽  
Henry W. Haslach
Keyword(s):  
Free Energy ◽  
Thermal Properties ◽  
Helmholtz Free Energy ◽  
Constitutive Models ◽  
Temperature Dependent ◽  
Thermal Inversion ◽  
Entropic Elasticity ◽  
Deformation Dependence ◽  
Constant Deformation ◽  
Inversion Effects

Abstract Existing thermoelastic constitutive models are not able to predict important thermal properties of rubbers. For example, the modified entropic elasticity theory fails to predict that the temperature coefficient of stress, the energetic contribution to the stress, and the specific heat at constant deformation depend on both deformation and temperature. A class of thermoelastic constitutive equations is proposed that generalizes given isothermal models and predicts the temperature and deformation dependence. The Helmholtz free energy is written as the sum of the isothermal energy function, but with temperature-dependent material moduli, and a function of temperature. Conditions on the Helmholtz energy are given to ensure that three inversion effects which characterize rubber are predicted. As an application, an isotropic, homogeneous, mechanically incompressible thermoelastic constitutive equation is generalized from the isothermal Mooney-Rivlin model. The three uniaxial thermal inversion effects are successfully reproduced by this model.

q-Deformed superstatistic thermodynamics in the presence of minimal length quantum mechanics

2019 ◽  
Vol 97 (10) ◽  
pp. 1161-1166 ◽  
Author(s):  
A.N. Ikot ◽  
U.S. Okorie ◽  
C.A. Onate ◽  
M.C. Onyeaju ◽  
H. Hassanabadi
Keyword(s):  
Heat Capacity ◽  
Free Energy ◽  
Quantum Mechanics ◽  
Thermodynamic Properties ◽  
Helmholtz Free Energy ◽  
Minimal Length ◽  
Quantum Oscillator ◽  
Length Scale ◽  
Boltzmann Factor ◽  
Minimal Length Scale

In this paper, we study the thermodynamic properties of a quantum oscillator in the presence of the minimal length scale in terms of the q-deformed superstatistics of statistical mechanics. We evaluated the partition function from the Boltzmann factor and obtained other thermodynamic properties such as internal energy, Helmholtz free energy, entropy, and specific heat capacity. We have also shown graphically the effects of the minimal length and the q-statistical properties on the thermodynamic properties of the system.

A canonical ensemble derivation of the McMillan-Mayer solution theory

1983 ◽  
Vol 48 (10) ◽  
pp. 2888-2892 ◽  
Author(s):  
Vilém Kodýtek
Keyword(s):  
Free Energy ◽  
Partition Function ◽  
Energy Function ◽  
Special Function ◽  
Helmholtz Free Energy ◽  
Canonical Ensemble ◽  
Free Energy Function ◽  
Solution Theory ◽  
Pure Solvent ◽  
The Common

A special free energy function is defined for a solution in the osmotic equilibrium with pure solvent. The partition function of the solution is derived at the McMillan-Mayer level and it is related to this special function in the same manner as the common partition function of the system to its Helmholtz free energy.

DFT study on the hydrolysis of metsulfuron-methyl: A sulfonylurea herbicide

2018 ◽  
Vol 17 (08) ◽  
pp. 1850050 ◽  
Author(s):  
Qiuhan Luo ◽  
Gang Li ◽  
Junping Xiao ◽  
Chunhui Yin ◽  
Yahui He ◽  
...  
Keyword(s):  
Free Energy ◽  
Water Molecule ◽  
Carbonyl Group ◽  
Energy Barrier ◽  
Density Functional ◽  
Free Energy Barrier ◽  
Functional Theory ◽  
Metsulfuron Methyl ◽  
Catalytic Role ◽  
Hydrolysis Of

Sulfonylureas are an important group of herbicides widely used for a range of weeds and grasses control particularly in cereals. However, some of them tend to persist for years in environments. Hydrolysis is the primary pathway for their degradation. To understand the hydrolysis behavior of sulfonylurea herbicides, the hydrolysis mechanism of metsulfuron-methyl, a typical sulfonylurea, was investigated using density functional theory (DFT) at the B3LYP/6-31[Formula: see text]G(d,p) level. The hydrolysis of metsulfuron-methyl resembles nucleophilic substitution by a water molecule attacking the carbonyl group from aryl side (pathway a) or from heterocycle side (pathway b). In the direct hydrolysis, the carbonyl group is directly attacked by one water molecule to form benzene sulfonamide or heterocyclic amine; the free energy barrier is about 52–58[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. In the autocatalytic hydrolysis, with the second water molecule acting as a catalyst, the free energy barrier, which is about 43–45[Formula: see text]kcal[Formula: see text]mol[Formula: see text], is remarkably reduced by about 11[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. It is obvious that water molecules play a significant catalytic role during the hydrolysis of sulfonylureas.

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