Stability of Sulfur Nitrides: A First-Principles Study

A systematic computational study on the structural, electronic, and bonding properties of binary sulfur nitrides has been performed using the projector augmented wave method based on density functional theory. The pressure–composition phase diagram of the S–N system has been established. The simulated pressure–temperature phase diagram and X-ray diffraction pattern of (SN)x explain the experimentally observed two-phase coexistence. The crystal structure of experimentally observed orthorhombic (SN)x is predicted. The high-pressure phase transition of (SN)x has been studied. Sulfur–sulfur interactions induced by localized sulfur 3pz electrons are found in the high-pressure phase of (SN)x. With increasing nitrogen composition, the coordination number of sulfur atoms increases from two to six in the S–N system. Furthermore, two nitrogen-rich sulfur nitrides SN2 and SN4 have been found at high pressure. SN4 exhibits a high energy density (2.66 kJ·g–1), which makes it potentially interesting for industrial appl...