  We compute the lattice-dynamical and thermal equation of state properties of
ferromagnetic bcc iron using the first principles linear response
linear-muffin-tin-orbital method in the generalized-gradient approximation. The
calculated phonon dispersion and phonon density of states, both at ambient and
high pressures, show good agreement with inelastic neutron scattering data. We
find the free energy as a function of volume and temperature, including both
electronic excitations and phonon contributions, and we have derived various
thermodynamic properties at high pressure and temperature. The thermal equation
of state at ambient temperature agrees well with diamond-anvil-cell
measurements. We have performed detailed investigations on the behavior of
various thermal equation of state parameters, such as the bulk modulus, the
thermal expansivity, the Anderson-Gruneisen parameter, the Gruneisen ratio, and
the heat capacity as function of temperature and pressure. A detailed
comparison has been made with available experimental measurements, as well as
results from similar theoretical studies on nonmagnetic bcc Tantalum.
