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Users Group Meeting 2012
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MedeA® Application Notes for Fundamental Research

Molecular Dynamics Simulation of Crystalline C₆₀ Buckminsterfullerene with MedeA and LAMMPS This application note provides an overview of the forcefield based simulation of crystalline C₆₀ (Buckminsterfullerene) using the LAMMPS molecular dynamics simulation package. The emphasis is on the overall philosophy of LAMMPS calculations in the MedeA® environment.	Elastic coefficients and moduli for cubic silicon carbide (β-SiC), corundum (α-Al₂O₃), and a tourmaline crystal (Schorl) The compressibility, tensile strength, and mechanical resistance to shear of a solid are related to the corresponding moduli (bulk, Young’s, and shear modulus), which are derived from the coefficients of elasticity. First-principles calculations of these fundamental mechanical properties give values of the same quality as experimental data, but at a substantially smaller effort and cost. This is demonstrated here for cubic silicon carbide, β-SiC, corundum, α-Al₂O₃, and a tourmaline with a fairly complex crystal structure. First-principles calculations are a valuable source for these fundamental materials property data.
Crystal Structure of Glucose: Placing Hydrogen Atoms by Computations The crystal structure of a purely organic, hydrogen-bonded molecular crystal is very well described by density functional theory with a gradient-corrected Perdew-Becke-Ernzerhof potential. The computations were preformed with the VASP program using the projector augmented wave method with a plane wave basis set. The agreement between computed and experimental lattice parameters is better than 2% with a tendency of the calculations to overestimate the bond lengths. The calculations provide equilibrium positions for the hydrogen atoms, which are difficult to place based on x-ray diffraction data.	Surface Energy of Molybdenum The surface energy of a material is defined as the energy required to create a surface (h k l) from the bulk material. Surface energies are usually given in units of J/m^{2^.}
Practical Thermochemistry: Sodium Metal, Chlorine Gas, and Solid Sodium Chloride This case study covers the practical use of MedeA® to calculate thermochemical functions for solids, molecules and atoms. We will use VASP and PHONON for this, but the current document focuses on the thermochemistry and not the details of the calculations.	Cleavage Energy of TiN The purpose of this study is the computation of the cleavage energy of a material, i.e. the energy required to split a material into two parts. This could be a bulk material, a grain boundary, or an interface. To this end, one needs to compute the total energy of the bulk solid and the material with a free surface.

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