arXiv subjects

A. Lang

Publications and source records attributed to A. Lang.

3 recordsLinked to original sources

arXiv2000

Exact Criterion for Determining Clustering vs. Reentrant Melting Behavior for Bounded Interaction Potentials

We examine in full generality the phase behavior of systems whose constituent particles interact by means of potentials which do not diverge at the origin, are free of attractive parts and decay fast enough to zero as the interparticle separation r goes to infinity. By employing a mean field-density functional theory which is shown to become exact at high temperatures and/or densities, we establish a criterion which determines whether a given system will freeze at all temperatures or it will display reentrant melting and an upper freezing temperature.

cond-mat.soft↗

arXiv2000

Fluid and solid phases of the Gaussian core model

We study the structural and thermodynamic properties of a model of point particles interacting by means of a Gaussian pair potential first introduced by Stillinger [Stillinger F H 1976 J. Chem. Phys. 65, 3968]. By employing integral equation theories for the fluid state and comparing with Monte Carlo simulation results, we establish the limits of applicability of various common closures and examine the dependence of the correlation functions of the liquid on the density and temperature. We employ a simple, mean-field theory for the high density domain of the liquid and demonstrate that at infinite density the mean-field theory is exact and that the system reduces to an `infinite density ideal gas', where all correlations vanish and where the hypernetted chain (HNC) closure becomes exact. By employing an Einstein model for the solid phases, we subsequently calculate quantitatively the phase diagram of the model and find that the system possesses two solid phases, face centered cubic and body centered cubic, and also displays reentrant melting into a liquid at high densities. Moreover, the system remains fluid at all densities when the temperature exceeds 1% of the strength of the interactions.

cond-mat.soft↗

arXiv1997

Stripe Correlations of Spins and Holes and Phonon Heat Transport in Doped La_2CuO_4

We present experimental evidence for a dramatic suppression of the phononic thermal conductivity of rare earth and Sr doped La_2CuO_4. Remarkably, this suppression correlates with the occurrence of superconductivity. Conventional models for the phonon heat transport fail to explain these results. In contrast, a straightforward explanation is possible in terms of static and dynamic stripe correlations of holes and spins.

cond-mat.supr-con↗