Temperature dependence in interatomic potentials and an improved potential for Ti

The process of deriving an interatomic potentials represents an attempt to integrate out the electronic degrees of freedom from the full quantum description of a condensed matter system. In practice it is the derivatives of the interatomic potentials which are used in molecular dynamics, as a model for the forces on a system. These forces should be the derivative of the free energy of the electronic system, which includes contributions from the entropy of the electronic states. This free energy is weakly temperature dependent, and although this can be safely neglected in many cases there are some systems where the electronic entropy plays a significant role. Here a method is proposed to incorporate electronic entropy in the Sommerfeld approximation into empirical potentials. The method is applied as a correction to an existing potential for titanium. Thermal properties of the new model are calculated, and a simple method for fixing the melting point and solid-solid phase transition temperature for existing models fitted to zero temperature data is presented.Comment: CCP 201

CAREM Project Status

CAREM is a CNEA (Comisión Nacional de Energía Atómica) project. This project consists of the development, design, and construction of a small nuclear power plant. First, a prototype of an electrical output of about 27 MW, CAREM 25, will be built in order to validate the innovation of the CAREM concept and then developed to commercial version. After several years of development, the CAREM Project reached such a maturity level that the Argentine government decided on the construction of CAREM prototype. Several activities are ongoing with the purpose of obtaining the construction permit for the CAREM prototype