High-energy-density materials (HEDMs) containing the cyclopentazole anion (cyclo-N5) are highly desirable due to the release of more energy and being environmentally more friendly than conventional HEDMs However the synthesis of stable cyclo-N5-containing HEDMs has been a challenge In this study quantum mechanical calculations were employed to elucidate the stability of [M(N5)2(H2O)4]·4H2O (M = Mn Fe Co and Zn) one of the few recently reported cyclo-N5-contained HEDMs under ambient conditions The results from our study indicate that the stability is due to the presence of two types of water (coordinated H2O (c-H2O) and hydrogen-bonded H2O (h-H2O)) Each type uses a unique mode to stabilize the highly reactive M(N5)2 cores c-H2O binds with M to reduce the M ? cyclo-N5 interaction leading to a less activated cyclo-N5 and higher kinetic barriers (Eas) for its decomposition In contrast h-H2O takes advantage of its permanent electrostatic interactions with cyclo-N5 to inhibit the decomposition The stabilizing effects of the two types of water on M(N5)2 are similar On the basis of the lower energy cost to remove h-H2O from the materials and the subsequent large decrease in the Ea due to this removal we propose that h-H2O acts as a “safety device” that prevents the materials from becoming kinetically unstable For future design of cyclo-N5-contained HEDMs we proposed the use of various molecular building blocks such as NH3 H2S which can tightly bind to M to reduce the M ? cyclo-N5 interaction and impose permanent electrostatic interactions with cyclo-N5 to provide the similar dual functions of H2O to suppress cyclo-N5 decomposition
Date of Award | 2019 |
---|
Original language | English |
---|
Supervisor | Mu-Jeng Cheng (Supervisor) |
---|
Dual functions of water in stabilizing metal-pentazolate hydrates [M(N5)2(H2O)4]·4H2O (M = Mn Fe Co and Zn) high-energy-density materials
正華, 羅. (Author). 2019
Student thesis: Doctoral Thesis