We Have Investigated the Structural Phase Transition and Thermophysical Properties of Ptn By Using Interaction Potential Model (Ipm). the Ipm Consists of Various Interaction Viz Coulomb Interaction, Three-Body Interaction (Tbi) and Overlap Repulsive Short Range Interaction. Our Theoretical Investigation Predicts the Structural Phase Transition of Ptn from B3 to B1 Structure. We Found B3 to B1 Phase Transition at 11 Gpa. at the Same Transition Pressure (11 Gpa) the Volume Drop Confirms the First Order Phase Transition. In Addition We Have Also Computed the Thermo Physical Properties I.E. Force Constant, Reststrahlen Frequency, Debye Temperature and Compressibility. These Thermophysical Properties Are New and Calculated In First Time. the Results Are In General Agreement With Available Theoretical Results Due to Unavailability of Experimental Data.