The new valence state [Ga]−5 in Li-Ga-Te system under high pressure

The density-functional theory is used to search for the candidate structures of Li-Ga-Te system below 100 GPa. Several new stable structures are uncovered, namely, P-3m1 LiGaTe2, P4/mmm Li9GaTe2, Immm Li9GaTe2. The band-gap of the I-42d LiGaTe2 and P4/mmm Li9GaTe2 corresponds to the peak position of the imaginary part of the dielectric function. Meanwhile, a new chemical valence of Ga atom under high pressure with [Ga]−5 ionic charge state is found. The dense accumulation of Li atoms and high pressure caused the change of valence state of Ga.