Metal free half metallic graphitic carbon nitride on BN layer

We have investigated structural, adsorptive, and magnetic properties of metal free graphitic carbon nitride ({\it g}-C$_4$N$_3$) layer on hexagonal BN layer (h-BN) using the optB88-vdW van der Waals density functional theory. The free standing {\it g}-C$_4$N$_3$ layer is known to have (2 $\times$ 2) surface reconstructed structure with 0.3 $\AA$ buckling feature. However, the surface reconstruction disappears on BN layer and the {\it g}-C$_4$N$_3$ layer becomes flat. Interestingly, the {\it g}-C$_4$N$_3$/BN hybridized system has a new lattice constant which differs from that of either BN or {\it g}-C$_4$N$_3$ and this lattice change is responsible for adsorption of {\it g}-C$_4$N$_3$ on BN layer. More surprisingly, we have observed half metallic behavior in {\it g}-C$_4$N$_3$ even on BN layer. We propose that our theoretical prediction can be verified using normal incidence of K-edge X-ray magnetic circular dichroism (XMCD) measurement and also our finding indicates that the {\it g}-C$_4$N$_3$/BN system can be utilized for novel metal free spintronics material.