ELECTRONIC STRUCTURE OF SIX PHASES OF C₃N₄: A THEORETICAL APPROACH

Abstract

A systematic study of the structural properties and electronic structure of six phases of C 3 N 4 is presented. The phases under study are the β, α, cubic, pseudocubic and two graphitic with different space group. The structural analysis shows that only in β and graphitic phases the N atoms behave in a pure sp 2 configuration. In the other phases, α, cubic and pseudocubic, the N with its 3 C neighbors form a pyramid. The band structure for each of the six phases is presented indicating with β, α and cubic phases have an indirect gap while the pseudocubic and the two graphitic phases have a direct gap. Also charge density contours are presented and analyzed.

Band gap of C3N4 in the GW approximation

“…3. At zero pressure, our results indicate an energy trend that is consistent with the previous results [2,34,59,60]. The heptazine-based phase has the lowest energy.…”

Electronic structure of Ge3N4 possible structures

“…The phase with highest density is the cubic and that with lowest density is the graphitic. The behavior of the density is similar to that predicted for the C 3 N 4 [5] except that in that case the α and β have the same density. From the total energies the β phase is the most stable, the α is only about 1 kcal/mol above; the other phases are much higher in energy.…”

Improvement of photocatalytic activity of high specific surface area graphitic carbon nitride by loading a co-catalyst

“…600 mg of original HSSA was immersed in tetrahydrofuran (THF) solution containing triruthenium dodecacarbonyl (Ru 3 (CO) 12 ) as the precursor of RuO 2 , and it was stirred at 333 K for 4 h. Then, the suspension was dried under reduced pressure to remove THF. After that, the powder was finally calcined at 573 K in air for 1 h. Finally, different weight ratios of RuO 2 -loaded HSSA were obtained.…”

“…Carbon nitride was reported to have several hypothetical phases including a, b, cubic, pseudocubic, and graphitic phases [12]. Under ambient conditions, graphitic carbon nitride (g-C 3 N 4 ) is regarded to be the most stable allotrope and has the smallest direct band gap due to the sp 2 hybridization of carbon and nitrogen forming pconjugated graphitic planes [12].…”

“…Carbon nitride was reported to have several hypothetical phases including a, b, cubic, pseudocubic, and graphitic phases [12]. Under ambient conditions, graphitic carbon nitride (g-C 3 N 4 ) is regarded to be the most stable allotrope and has the smallest direct band gap due to the sp 2 hybridization of carbon and nitrogen forming pconjugated graphitic planes [12]. Meanwhile, g-C 3 N 4 can be easily obtained by polymerization of cyanamide, dicyandiamide, or melamine [13], and it is successfully applied to Friedel-Crafts reactions [14], the electrocatalytic activity [15], and photocatalytic water splitting with an appropriate electron donor [16].…”