Full Charge Density Technique

Abstract

According to the Hohenberg-Kohn variational principle [1], the total energy functional is stationary for small density variations around the equilibrium density. Therefore, a reasonably accurate trial density is suitable to determine the total energy of the system within an error which is second order in the difference between the trial and equilibrium charge densities. This recognition has led to the elaboration of the Full Charge Density (FCD) technique [44, 45, 48, 49] as an alternative to the full-potential methods. The FCD technique is designed to maintain high efficiency but at the same time to give total energies with an accuracy similar to that of the full-potential methods. It assumes the knowledge of just the spherically symmetric part of the potential but at the same time makes use of the full non-spherically symmetric charge density. In recent years it turned out that results obtained from such a technique compare very well to those of full potential methods. Today many research groups adopt this technique in combination with a muffin-tin type of method rather than the formally exact but very demanding full-potential approach [42, 43, 44, 45, 77, 92, 93].