  We present a general and convenient first principle method to study
near-field radiative heat transfer. We show that the Landauer-like expression
of heat flux can be expressed in terms of a frequency and wave-vector dependent
macroscopic dielectric function which can be obtained from the linear response
density functional theory. A random phase approximation is used to calculate
the response function. We computed the heat transfer in three systems --
graphene, molybdenum disulfide (MoS$_2$), and hexagonal boron nitride (h-BN).
Our results show that the near-field heat flux exceeds the blackbody limit up
to four orders of magnitude. With the increase of the distances between two
parallel sheets, a $1/d^2$ dependence of heat flux is shown, consistent with
Coulomb's law. The heat transfer capacity is sensitive to the dielectric
properties of materials. Influences from chemical potential and temperature are
also discussed. Our method can be applied to a wide range of materials
including systems with inhomogeneities.
