An ab initio based tight-binding molecular-dynamics method is used to gener
ate 60 amorphous carbon nitride structures, a-CN, with various stoichiometr
ies and densities, providing the first atomic level insight into the chemic
al bonding properties of these materials. Focusing on high densities, we ob
serve clear trends counteracting the formation of a low-compressibilty phas
e: (i) N-incorporation strongly catalyzes C-undercoordination, which in tur
n (ii) causes the nitrogens to develop paracyanogen-like (CN-double and -tr
iple) bonding. (iii) The most favorable densities for a-CN occur to be much
lower than the desired hard crystalline ones. (C) 1999 Published by Elsevi
er Science Ltd. All rights reserved.