Spin-orbit coupling in the actinide elements: A critical evaluation of theoretical equilibrium volumes - art. no. 035103

The difficulty of converging the contribution of the spin-orbit interaction to the total energy within an ls basis in actinide electronic structure ca lculations is discussed in detail. In particular, it is demonstrated that t he source of the poor convergence is the treatment of the actinide 6p state s. The limitation of the standard approach to relativity in full potential methods is manifested in muffin-tin based methods by a dependence of the to tal energy on the choice of muffin-tin radius. Despite this limitation it i s found that structural phase stabilities are not affected, nor are pressur e induced phase transitions. In order to treat the relativistic spin-orbit coupling in as large a part of space as possible one should, in muffin-tin based calculations, use a radius that is touching, or near touching, for al l calculated volumes.