Search results for "Equilibrium"
showing 10 items of 1021 documents
Fluctuation theorems for non-Markovian quantum processes
2013
Exploiting previous results on Markovian dynamics and fluctuation theorems, we study the consequences of memory effects on single realizations of nonequilibrium processes within an open system approach. The entropy production along single trajectories for forward and backward processes is obtained with the help of a recently proposed classical-like non-Markovian stochastic unravelling, which is demonstrated to lead to a correction of the standard entropic fluctuation theorem. This correction is interpreted as resulting from the interplay between the information extracted from the system through measurements and the flow of information from the environment to the open system: Due to memory e…
Equilibrium Geometry of the Ethynyl (CCH) Radical
2004
The equilibrium geometry of the ethynyl (CCH) radical has been obtained using the results of high-level quantum chemical calculations and the available experimental data. In a purely quantum chemical approach, the best theoretical estimates (1.208 A for r C C and 1.061-1.063 A for r C H ) have been obtained from CCSD-(T), CCSDT, MR-AQCC, and full CI calculations with basis sets up to core-polarized pentuple-zeta quality. In a mixed theoretical-experimental approach, empirical equilibrium geometrical parameters (1.207 A for r C C and 1.069 A for r C H ) have been obtained from a least-squares fit to the experimental rotational constants of four isotopomers of CCH which have been corrected fo…
Non-Equilibrium Thermodynamics of Unsteady Superfluid Turbulence in Counterflow and Rotating Situations
2005
The methods of nonequilibrium thermodynamics are used in this paper to relate an evolution equation for the vortex line density $L$, describing superfluid turbulence in the simultaneous presence of counterflow and rotation, to an evolution equation for the superfluid velocity ${\mathbf{v}}_{s}$, in order to be able to describe the full evolution of ${\mathbf{v}}_{s}$ and $L$, instead of only $L$. Two alternative possibilities are analyzed, related to two possible alternative interpretations of a term coupling the effects of the counterflow and rotation on the vortex tangle, and which imply some differences between situations where counterflow and rotation vectors are parallel or orthogonal …
Energy and temperature of superfluid turbulent vortex tangles
2007
We consider three aspects of turbulent vortex tangles in superfluids. First, we outline some contributions to the Vinen’s equation for the time evolution of the vortex line density, related to the presence of pinned vortices incorporating the effects of the walls. Afterwards, we analyze some aspects of the energy balance of the vortex tangle, related to frictional dissipation and to vortex formation and destruction. Finally, we explore the concept of an effective temperature for the vortex tangle, related to the average energy of the vortex loops and to the diffusion coefficient of vortex lines. The combination of these ideas suggests some formal similarities with other kinds of driven none…
Nonequilibrium critical scaling in quantum thermodynamics
2016
The emerging field of quantum thermodynamics is contributing important results and insights into archetypal many-body problems, including quantum phase transitions. Still, the question whether out-of-equilibrium quantities, such as fluctuations of work, exhibit critical scaling after a sudden quench in a closed system has remained elusive. Here, we take a novel approach to the problem by studying a quench across an impurity quantum critical point. By performing density matrix renormalization group computations on the two-impurity Kondo model, we are able to establish that the irreversible work produced in a quench exhibits finite-size scaling at quantum criticality. This scaling faithfully …
Heavy quark momentum diffusion coefficient in 3D gluon plasma
2020
We study the heavy-quark momentum diffusion coefficient in far from equilibrium gluon plasma in a self-similar regime using real-time lattice techniques. We use 3 methods for the extraction: an unequal time electric field 2-point correlator integrated over the time difference, a spectral reconstruction (SR) method based on the measured equal time electric field correlator and a kinetic theory (KT) formula. The time-evolution of the momentum diffusion coefficient extracted using all methods is consistent with an approximate $t^{\frac{-1}{2}}$ power law. We also study the extracted diffusion coefficient as a function of the upper limit of the time integration and observe that including the in…
Determination of the stress distribution at the interface metal-oxide: Numerical and theoretical considerations
2005
In this paper we give a brief presentation of the approaches we have recently developed on the oxidation of metals. Firstly, we present an analytical model based on non-equilibrium thermodynamics to describe the reaction kinetics present during the oxidation of a metal. Secondly, we present the molecular dynamics results obtained with a code specially tailored to study the oxidation and growth of an oxide film of aluminium. Our simulations present an excellent agreement with experimental results.
Calculation of the rate constants for hydrogen abstraction reactions by Hydroperoxyl radical from Methanol, and the investigation of stability of CH3…
2020
Abstract Master equation (ME) with Lennard-Jones potential utilized to simulate the collision between CH3OH and HO2 radical in the presence of bath gas. The reaction mechanism explored through the lowest doublet potential energy surface at CCSD(T)/aug-cc-pVTZ//B3LYP/aug-cc-pVTZ level of theory that is barrierless and forms shallow energized intermediate at the entrance channel. The investigation of the fractional population showed that lifetime of CH3OH.HO2 intermediate (INT*) is fairly short due to its shallow depth, and at the low temperature, most reaction takes place by re-dissociation back to reactants and also when the pressure is high enough, the INT* is thermalized and comes into eq…
Disequilibrium melt distribution during static recrystallisation
2004
Melt migration and segregation, and the rheology of partially molten rocks in the upper mantle and lower crust, strongly depend on the grain-scale distribution of the melt. Current theory for monomineralic aggregates predicts a perfectly regular melt framework, but high-temperature experiments with rock-forming minerals + melt show considerable deviations from this predicted geometry. Disequilibrium features, such as fully wetted grain boundaries and large melt patches, have been described; these were mainly attributed to surface-energy anisotropy of the minerals. We present static analogue experiments with norcamphor + ethanol that allow continuous in situ observation of the evolving liqui…
Adsorption of Heavy Metals from Aqueous Solutions onto Activated Carbon in Single Cu and Ni Systems and in Binary Cu-Ni, Cu-Cd and Cu-Zn Systems
1997
Single copper and nickel adsorption from aqueous solutions onto a granular activated carbon is reported. Metal removals increase on raising pH and temperature, and decrease on raising the initial metal concentration at constant carbon dose. The adsorption processes are modelled using the surface complex formation (SCF) Triple Layer Model (TLM) with an overall surface bidentate species. A dependence of the SCF constant on pH, initial molar metal/carbon ratio and temperature is observed, and a correlation for log Kads is determined. The SCF model successfully predicts copper and nickel removals in single metal solutions. Adsorption in the binary metal systems copper–nickel, copper–cadmium and…