Mechanical properties of doped g-C3N4 – A first-principle study

• The mechanical properties of doped g-C3N4 systems were evaluated by first-principles for the first time.
• Hexagonal-orthorhombic structural transition caused by B, P and S doping occurred in g-C3N4.
• The optimal carbon self-doping is more stable than B, P and S doping.
• The shear modulus GV of g-C3N4 declines after doping with C, B, P and S impurities.

As a nonmetallic catalyst, graphite-like C3N4 has attracted widespread interest during past decades. Various methods included doping have been applied to improve the photocatalytic activity of g-C3N4. In this work, the structural and elastic properties of pristine g-C3N4 and doped structures were investigated using first-principles calculations. The empirical equation of states for solids (EOS) was used to compute the bulk modulus. The independent elastic constants of pure g-C3N4 and doped structures, together with the shear modulus, Young's modulus and Poisson's ratio, were also examined. It was found that the bulk modulus of g-C3N4 change slightly when doped with C and B atoms but reduce apparently with S and P doping. Moreover, the shear modulus and Young's modulus reduce greatly after doping, though the ductility and brittleness remain unchanged after doping. It should be pointed out that understanding the mechanical properties of the doped materials will have practical guidance in the subsequent application.