  The purpose of this work is to present accurate and detailed mass-radius
relations for white dwarf (WD) models with helium, carbon, oxygen, silicon and
iron cores, by using a fully updated stellar evolutionary code. We considered
masses from 0.15 to 0.5 Mo for the case of helium core, from 0.45 to 1.2 Mo for
carbon, oxygen and silicon cores and from 0.45 to 1.0 Mo for the case of an
iron core. In view of recent measurements made by Hipparcos that strongly
suggest the existence of WDs with an iron-dominated core, we focus our
attention mainly on the finite-temperature, mass-radius relations for WD models
with iron interiors. Furthermore, we explore the effects of gravitational,
chemical and thermal diffusion on low-mass helium WD models with hydrogen and
helium envelopes.
