  We present an investigation on effect of the ion-neutral (or ambipolar)
diffusion heating rate on thermal phases of a molecular cloud. We use the
modeling of ambipolar diffusion with two-fluid smoothed particle hydrodynamics,
as discussed by Nejad-Asghar & Molteni. We take into account the ambipolar
drift heating rate on the net cooling function of the molecular clouds, and we
investigate the thermal phases in a self-gravitating magnetized one dimensional
slab. The results show that the isobaric thermal instability criterion is
satisfied in the outer parts of the cloud, thus, these regions are thermally
unstable while the inner part is stable. This feature may be responsible for
the planet formation in the outer parts of a collapsing molecular cloud and/or
may also be relevant for the formation of star forming dense cores in the
clumps.
