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Layered perovskite Ruddlesden Popper (RP) transition metal oxides are interesting because of the effects of their 2 dimensional crystal structure on their lattice response, as well as electronic and optical properties. The Stannate Sr₂SnO₄ has the K₂NiF₄ type RP structure at high temperatures, but undergo multiple structural phase transitions as the temperature is lowered. In this talk, we present our first principles Density Functional Theory results that elucidate the mechanism behind these phase transitions. We discuss the details of the octahedral tilting and examine its effects on the electronic and optical properties of Sr₂SnO₄.