A Practical Way to Develop the Orbital-free Density Functional Calculations

Aims: For modeling of large polyatomic systems one may use the variation principle for energy density functional. The key point to make this is to find the functional of kinetic energy in the orbital-free approach.

Study Design: We describe a way to find functionals of kinetic energy for single atoms and to use them for modeling of polyatomic systems. On examples of diatomic systems Si2, Al2, and P2 the equilibrium interatomic distances and binding energies were calculated in good comparison with published data. Results for Si-Al, Si-P and Al-P dimers are also close to results of Kohn-Sham calculations.

Place and Duration of Study: Institute of Materials, Khabarovsk, Russia; Institute of Applied Mathematics, Khabarovsk, Russia; 2011-2013.

Methodology: We worked in the frameworks of pseudo potentials and the local density approximation of the density functional theory. We used the Kohn-Sham calculations as start steps to find the kinetic energy functionals for single atoms (Al, Si, P). Then we constructed the total energy functionals for dimers and calculated equilibrium interatomic distances and the binding energies.

Results: We constructed the total energy functional for a dimer Si2 and minimized it with some parameters in order to obtain the equilibrium interatomic distance and the binding energy in good comparison with published data. Then we modeled Al2, P2, Si-Al, Si-P, and Al-P dimers with the same parameters and also obtained good results.

Conclusion: We have demonstrated a principal possibility to find equilibrium densities, interatomic distances and binding energies in the orbital-free approach using the kinetic energy functionals for single atoms calculated by the Kohn-Sham method.