If you don't care about the safety of anyone involved and don't wish to go into a government building with your laptop, I'm sure thermite would be a lot more effective for its weight than a civilian acquirable explosive.

A thin layer of thermite, a magnesium starter, and a ceramic holster to keep the thermite firmly against the drive during the burn should work. Two thousand degrees of burning iron a few millimeters away from the nand should thoroughly annihilate it.

A high voltage surge would be simpler to implement.

Might not be the best think to take with you when you board a plane.

Do they check the internals of a laptop's hard drive nowadays? :-)

chemical scans probably will detect it.

Chemical scans would probably be pretty hard-pressed to detect thermite, which is after all just aluminium and iron oxide powder. Even the magnesium starter is non-sniffable.