The decompression process of CaSiO_3 perovskite was studied with molecular dynamics (MD) simulation from high pressure to negative pressure. The computed equation of state for CaSiO_3 is in good agreement with the experimental data and the results of the MD simulation reported. The computed bulk modulus is within the range of the experimental data. The results of our MD simulation on decompression and recompression are similar to the experimental results. There are two stages in the collapse of CaSiO_3 perovskite under decompression: the breakage of SiO_6 octahedron and the breakage of CaO_(12) icosahedron. If the Ca-O icosahedron has not been destroyed, the collapsed CaSiO_3 perovskite on decompression can be recovered on recompression. If the Ca-O icosahedron has been destroyed, it is not recoverable on recompression. This is a new result in our MD simulation. The infrared spectrum of CaSiO3 perovskite has been calculated with MD data. It is shown that the non-crystallization of CaSiO_3 perovskite on decompression is a second transition of softening mode and kinetically controlled metastable process. It is well obeyed that there is an isochoris metastable limit in CaSiO_3 perovskite and the quadratic law (P - P_s) ～ ( V - V_s)~2.

Key words: PEROVSKITE TYPE STRUCTURE, CALCIUM SILICATE, AMORPHOUS, IR