Please file the RTI application in the Chandigarh Muncipality with the concerned PIO with the prescribed fee. The Chandigarh Muncipal Corporation is established by The Punjab Municipal Corporation Act, 1976, hence its a public authourity as per sec 2(h) of RTI act 2005.
To sum it up you can file RTI with the Chandigarh Muncipal Corporation with the prescribed fee to get death certificate as per RTI act.
For more info please check https://onlinerti.com/