arXiv subjects

J. Christian Schoen

Publications and source records attributed to J. Christian Schoen.

4 recordsLinked to original sources

arXiv2015

Ab initio computation of the transition temperature of the charge density wave transition in TiSe2

We present a density functional perturbation theory approach to estimate the transition temperature of the charge density wave transition of TiSe2. The softening of the phonon mode at the L-point where in TiSe2 a giant Kohn anomaly occurs, and the energy difference between the normal and distorted phase are analyzed. Both features are studied as function of the electronic temperature, which corresponds to the Fermi-Dirac distribution smearing value in the calculation. The transition temperature is found to be 500 K and 600 K by phonon and energy analysis, respectively, in reasonable agreement with the experimental value of 200 K.

cond-mat.mtrl-sci↗

arXiv1999

Energy and entropy of metastable states in glassy systems

We investigate the multi-valley energy landscape of a 3-D on-lattice network model for covalent glasses, numerically determining the shape of the valleys, the local density of states, the density of minima and the local connectivity. We present some of these quantities in a graphical birds-eye view of the landscape, and discuss their implications for the relaxation dynamics and cooling behavior of glasses. The strong similarities between the landscape of this model and those of other complex systems point to the possibility of a common low-temperature dynamical description.

cond-mat.stat-mech↗

arXiv1998

The lid method for exhaustive exploration of metastable states of complex systems

The `lid' algorithm performs an exhaustive exploration of neighborhoods of local energy minima of energy landscapes. This paper describes an implementation of the algorithm, including issues of parallel performance and scalability. To illustrate the versatility of the approach and to stress the common features present in landscapes of quite different systems, we present selected results for 1) a spin glass, 2) a ferromagnet, 3) a covalent network model for glassy systems, and 4) a polymer. The exponential nature of the local density of states found in these systems and its relation to the ordering transition is briefly commented upon.

physics.comp-ph↗

arXiv1998

Properties of the energy landscape of network models for covalent glasses

We investigate the energy landscape of two dimensional network models for covalent glasses by means of the lid algorithm. For three different particle densities and for a range of network sizes, we exhaustively analyse many configuration space regions enclosing deep-lying energy minima. We extract the local densities of states and of minima, and the number of states and minima accessible below a certain energy barrier, the 'lid'. These quantities show on average a close to exponential growth as a function of their respective arguments. We calculate the configurational entropy for these pockets of states and find that the excess specific heat exhibits a peak at a critical temperature associated with the exponential growth in the local density of states, a feature of the specific heat also observed in real glasses at the glass transition.

cond-mat.stat-mech↗