Monatomic structures of B, C, N, and O: First-principle study of relative stabilities and bulk moduli

The calculations based on the first-principles were used to determine the relative stabilities and bulk moduli of monatomic structures of B, C, N and O with different coordination numbers. All the elements were observed to be loosely packed cubic diamond (CD) structure at low pressure and at high pressure, moderately packed simple cubic (SC) structure. Due to the four valence electrons in C, the CD structure was found to be greatly stabilized by the extensive overlap of bonded electrons. It was also found that C possessed smallest atomic volume of the four elements and formed the CD structure with the highest bulk modulus of all structures.