The efficiency of the LAPW basis derives from its use of carefully chosen representations of the wavefunctions in different regions. In particular, a spherical harmonics expansion on a radial mesh is used inside the spheres and a planewave expansion outside. With this choice, rapid variations of the wavefunctions inside the spheres pose no particular problems, and accordingly the method is well suited to all-electron calculations (i.e. no pseudopotential) as well as d- and f-electron materials. However, rapidly varying wavefunctions imply rapidly varying charge densities and potentials, and this requires that the representations of the charge density and potential be equally flexible.
KeywordsCharge Density Core State Secular Equation Reciprocal Lattice Vector Total Energy Calculation
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