. 2015 May 6;5:9870. doi: 10.1038/srep09870

Table 1. Hardness (GPa), computed by microscopic models, enthalpy of formation (EF) (eV/atom), and atomic density (atoms/Å³) for diamond and stable C-N phases at zero pressure.

Structures	EF	density	Hardness (GPa)
Structures	EF	density	Oganov	Šimůnek	Gao	Others
Diamond		0.176	89.2	90.7	93.0	93.6^a
	0.813	0.167	85.6	89.0	82.2	77.4^b
P31c-C₃N₄	0.504	0.161	78.1	81.3	72.0	82.7^c
Cm-C₃N₄	0.571	0.165	75.5	82.0	71.7
	0.602	0.167	80.2	83.0	70.5
	0.710	0.173	83.8	86.8	75.1	92^c
Cmc2₁-C₃N₄	0.644	0.167	79.1	76.1	72.7
P4₂/m-CN	0.395	0.155	58.3	70.5	54.7
Pnnm-CN	0.422	0.160	59.6	72.7	57.0	62.3^d

^aReference³⁸. ^bReference¹¹. ^cReference²¹.^dReference³².

Table 1. Hardness (GPa), computed by microscopic models, enthalpy of formation (EF) (eV/atom), and atomic density (atoms/Å3) for diamond and stable C-N phases at zero pressure.