where Ti x P y S z is the formula for the structure 𝑆 0 𝐶 , a i is the proportion of the material Ti xi P yi S zi to which Ti x P y S z decomposes, and E[Ti xi P yi S zi ] is the total energy per formula unit of the stable structure Ti xi P yi S zi . The stoichiometry must balance the number of Ti, P and S atoms. Hence, a positive E h indicates that the structure is unstable. This calculation procedure for E h made two assumptions: (1) there are absolutely no stable phases within the space {Ti, P, S} that can ever be found, otherwise such phases would appear in the right side of Eq. 1, and (2) all the stable phases within the 6 chemical sub-spaces ({Ti, P}, {Ti, S}, {P, S}, {Ti}, {P} and {S}) have been identified. In the following, we question these assumptions.