Deriving the energy-volume equations of state EOS for Ca2PtO4 in Ca2IrO4-type and in K2NiF4-type (knf) structures, leads to energy destabilization at a larger volume for the latter and to propose the former as a post-K2NiF4-pknf-occurring at high pressures with a reduced dimensionality 2D-knf --> 1D-pknf and a rearrangement of the PtO6 octahedra from corner sharing in knf to edge sharing in pknf. Bader charge analysis indicates an increased covalence of Pt-O bond with such a transformation. The lowered dimensionality is also illustrated from the density of states. (C) 2010 Elsevier B. V. All rights reserved.