Structural and electronic properties of 9R diamond polytype

The electronic and structural properties of 9R diamond are studied by performing density functional (DFT) calculations, and compared with those of four other known polytypes (2H, 3C, 4H, and 6H). The calculated lattice constants, the unit cell energy, and the relative stability of these polytypes all agree well with the experimental sequence of diamond polytypes. It is found that the band gap of the cubic structure is considerably smaller than that of other polytypes. The trend of band gap increasing with the increase of hexagonality that has been found by others with other polytypes is not applicable to 9R polytype.