  Recently discovered class of 2D materials based on transition metal
phosphorous trichalcogenides exhibit antiferromagnetic ground state, with
potential applications in spintronics. Amongst them, FePS$ _{3} $ is a Mott
insulator with a band gap of $\sim$ 1.5 eV. This study using Raman spectroscopy
along with first-principles density functional theoretical analysis examines
the stability of its structure and electronic properties under pressure. Raman
spectroscopy reveals two phase transitions at 4.6 GPa and 12 GPa marked by the
changes in pressure coefficients of the mode frequencies and the number of
symmetry allowed modes. FePS$_3$ transforms from the ambient monoclinic C2/m
phase with a band gap of 1.54 eV to another monoclinic C2/m (band gap of 0.1
eV) phase at 4.6 GPa, followed by another transition at 12 GPa to the metallic
trigonal P-31m phase. Our work complements recently reported high pressure
X-ray diffraction studies.
