The speaker says the Cohen–Sham work offered a practical method for approximating quantum-mechanical properties of materials.

“Yeah, which is amazing because charge density is just this three-dimensional object, whereas the Hilbert space and wave functions are exponential. Um so that was a really interesting observation and then Cohen published another paper, I think with his post-doc uh Sham, Cohen-Sham uh wave functions kind of had a practical way to solving s”

“Some approximation of quantum mechanical properties of materials.”