A many-body force field was developed, for Ta, which was based upon extensive ab initio quantum mechanical calculations. It was used to calculate the zero-temperature equation of state for body-centered cubic, face-centered cubic and hexagonal close-packed crystal structures at pressures of up to 500GPa. A mixed-basis pseudopotential method was used to calculate the volume-relaxed vacancy formation energy as a function of pressure. In developing the force field, use was also made of previous quantum mechanical calculations of the equation of state for the A15 structure, of the surface energy of body-centered cubic (100) and of the energetics of shear twinning in a body-centered cubic crystal. It was found that, by using appropriate parameters, an embedded atom model force-field could reproduce all of these quantum mechanical data.

First-Principles Force Field for Metallic Tantalum. A.Strachan, T.Çagin, O.Gülseren, S.Mukherjee, R.E.Cohen, W.A.Goddard: Modelling and Simulation in Materials Science and Engineering, 2004, 12[4], S445-59