The anatase crystal structure is tetragonal sspace group I41 /amdd with two TiO2 units in the primitive cell, giving six Raman-active fundamentals in the vibrational spectrum: three Eg modes centered around 144, 197, and 639 cm−1 sdesignated here Eg(1), Eg(2), and Eg(3), respectivelyd, two B1g modes at 399 and 519 cm−1 sdesignated B1g(1) and B1g(2d), and an A1g mode at 513 cm−1.