“…Presence of indirect band gaps with gap openings in the range 0.94–1.81 eV may render their applications in photovoltaics. 92–96 In this connection it may be relevant to mention that while the PBE functional is known to underestimate the E g values of the systems in general, 14,33–36,40,41,43 the HSE06 functional on the other hand can predict the E g values of the compounds in close agreement with the experimental observations. 14,33,40,45,97 The HSE06 XC energy functional ( E HSE06 XC ) is mathematically expressed as: 98 E HSE06 XC = 1/4 E HF, SR X ( ω ) + 3/4 E PBE, SR X ( ω ) + E PBE, LR X ( ω ) + E PBE C where “X”, “C”, “SR” and “LR” symbolize the exchange, correlation, short range and long range terms respectively in the energy functional.…”