  Aims. With our time-dependent model atmosphere code PHOENIX, our goal is to
simulate light curves and spectra of hydrodynamical models of all types of
supernovae. In this work, we simulate near-infrared light curves of SNe Ia and
confirm the cause of the secondary maximum. Methods. We apply a simple energy
solver to compute the evolution of an SN Ia envelope during the free expansion
phase. Included in the solver are energy changes due to expansion, the energy
deposition of {\gamma}-rays and interaction of radiation with the material.
Results. We computed theoretical light curves of several SN Ia hydrodynamical
models in the I, J, H, and K bands and compared them to the observed SN Ia
light curves of SN 1999ee and SN 2002bo. By changing a line scattering
parameter in time, we obtained quite reasonable fits to the observed
near-infrared light curves. This is a strong hint that detailed NLTE effects in
IR lines have to be modeled, which will be a future focus of our work.
Conclusions. We found that IR line scattering is very important for the
near-infrared SN Ia light curve modeling. In addition, the recombination of Fe
III to Fe II and of Co III to Co II is responsible for the secondary maximum in
the near-infrared bands. For future work the consideration of NLTE for all
lines (including the IR subordinate lines) will be crucial.
