2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/28012Curvilinear coordinates, first introduced by F. Gygi for valence-only electronic systems within the local-density functional theory, can be used to describe both core and valence electrons in electronic-structure calculations. A simple and quite general coordinate transformation results in a large, yet affordable plane-wave energy cutoff for full-core systems (e.g., about 120 Ryd for carbon or silicon) within the local-density functional theory, and in a reduced correlation time for full-core variational Monte Carlo calculations. Numerical tests for isolated Li, C, and Si atoms are presented.14 pages, 8 Postscript figures; acknowledgements and two refs. addedMaterials Sciencetext