  Using density functional theory with the inclusion of van der Waals (vdW)
interaction, we have investigated electronic energy bands, density of states,
effective masses of charge carriers, and photo absorption coefficients of
pseudo-cubic CH$_3$NH$_3$PbX$_3$ (X=I, Br). Our results confirm the direct
bandgap of 1.49 (1.92) eV for X=I (Br) in the pseudo-cubic $Pm$ phase with
lattice constant of 6.324 (5.966) \AA, being agreed well with experiment and
indicating the necessity of vdW correction. The calculated photo absorption
coefficients for X=I (Br) have the onset at red (orange) color and the first
peak around violet (ultraviolet) color in overall agreement with the
experiment.
