arXiv subjects

Anja Kuhnhold

Publications and source records attributed to Anja Kuhnhold.

4 recordsLinked to original sources

arXiv2026

Thermodynamic state variables from a minimal set of quantum constituents

We show how the macroscopic state variables pressure, entropy and temperature of equilibrium thermodynamics can be consistently derived from the (quantum) chaotic spectral structure of one or two particles in two-dimensional domains. This provides a definition of work and heat from first principles, a microscopic underpinning of the first and second law of thermodynamics, and a transparent illustration of the ``eigenstate thermalization hypothesis''.

quant-ph↗

arXiv2025

Thermodynamics of Hard Sphere and Spherocylinder Mixtures -- Scaled Particle Theory and Monte Carlo Simulations

We review the literature on scaled particle theory (SPT) and its extensions and discuss results applied to describe the thermodynamics of hard particle mixtures. After explaining the basic concepts of scaled particle theory to compute the free energy of immersing a particle into a mixture, examples are discussed for the simple case of a hard sphere dispersion and the free volume fraction of ghost spheres in a hard sphere dispersion. Next, the concept is applied to mixtures, and general expressions are shown that relate the free volume fraction in mixtures to the key thermodynamic properties, such as the chemical potential(s) and (osmotic) pressure. Subsequently, it is revealed how these concepts can be extended towards multi-component systems. It is shown that free volume fractions provide chemical potentials and total pressure of multi-component mixtures, and thereby yield the full equation of state. We present novel results for ternary particle dispersions composed of hard spherocylinders and two types of hard spheres differing in size. Throughout, we show the accuracy of SPT by comparing the results with those of Monte Carlo computer simulations.

cond-mat.soft↗

arXiv2023

Equation of State of Charged Rod Dispersions

We study the accuracy of the theory of Stroobants, Lekkerkerker and Odijk, called SLO theory (Macromolecules 19 (1986) 2232-2238), to describe the thermodynamic properties of an isotropic fluid of charged rods. By incorporation of the effective diameter of the rods according to SLO theory into scaled particle theory (SPT) we obtain an expression for the rod concentration-dependent free volume fraction and the osmotic pressure of a collection of charged hard spherocylinders. The results are compared to Monte Carlo simulations. We find close agreement between the simulation results and the SLO-SPT predictions for not too large values of the Debye length and for high rod charge densities. The deviations increase with rod density, particularly at concentrations above which isotropic-nematic phase transitions are expected.

cond-mat.soft↗

arXiv2019

Reconsidering the structure of nucleation theories

We discuss the structure of the equation of motion that governs nucleation processes at first order phase transitions. From the underlying microscopic dynamics of a nucleating system, we derive by means of a non-equilibrium projection operator formalism the equation of motion for the size distribution of the nuclei. The equation is exact, i.e. the derivation does not contain approximations. To assess the impact of memory, we express the equation of motion in a form that allows for direct comparison to the Markovian limit. As a numerical test, we have simulated crystal nucleation from a supersaturated melt of particles interacting via a Lennard-Jones potential. The simulation data show effects of non-Markovian dynamics.

cond-mat.stat-mech↗