Carbon Nitride Frameworks and Dense Crystalline Polymorphs

13 Aug 2016  ·  Pickard Chris J., Salamat Ashkan, Bojdys Michael J., Needs Richard J., McMillan Paul F. ·

We used ab initio random structure searching (AIRSS) to investigate polymorphism in C3N4 carbon nitride as a function of pressure. Our calculations reveal new framework structures, including a particularly stable chiral polymorph of space group P43212 containing mixed sp2 and sp3-bonding, that we have produced experimentally and recovered to ambient conditions... As pressure is increased a sequence of structures with fully sp3-bonded C atoms and three-fold coordinated N atoms is predicted, culminating in a dense Pnma phase above 250 GPa. Beyond 650 GPa we find that C3N4 becomes unstable to decomposition into diamond and pyrite-structured CN2. read more

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Materials Science