Effective mass is actually the mass of these charge carriers (e-/h+) whence they respond to any type of interaction in a crystal lattice. The effective mass highly depend on the crystal structure or electronic band structure of solid. E.g. TiO2 usually exists in three polymorphs forms, anatase, rutile and brookite. Mostly the anatase is reported as the indirect band gap while rutile and brookite as direct band gap semiconductors and comparatively anatase shows highest lifetime for excited electrons or you can say in anatase the electrons have lightest average effective mass because of fast migration in the crystal lattice.

I thin density function theory can help you to determine the effective mass of TiO2 .

I agree with Rayees Ahmad Rather .

thanks Dr. ahmed Rather and Dr.luma ahmed

in general the effective mass is depending on the crystal structure and electronic band structure of solid.