Thermal stability of cubane C8H8

Abstract

The reasons for the anomalously high thermal stability of cubane C8H8 and the mechanisms of its decomposition are studied by numerically simulating the dynamics of this metastable cluster at T = 1050 - 2000 K using a tight-binding potential. The decomposition activation energy is found from the temperature dependence of the cubane lifetime obtained from the numerical experiment; this energy is fairly high, Ea = 1.8 - 2.0 eV. The decomposition products are, as a rule, either C6H6 and C2H2 molecules or the isomer C8H8 with a lower energy.Comment: 5 figure

Thermal stability of hexaprismane C12H12 and octaprismane C16H16

“…These results agree well with our data found using the DFT (B3LYP/6 311G): 4.50 and 4.40 eV/atom for hexaprismane and octaprismane, respectively. We note that the binding energy of cubane that we previously found in the tight binding model [19] was 4.42 eV/atom [26], which indicates an increase in thermodynamic stability of hexaprismane and octaprismane compared with cubane. However, it was shown below, this is not accompanied by an increase in the kinetic stability.…”

“…Since the total energy remains constant during the system evolution, its microcanonical temperature T (as the measure of the kinetic energy) increases after the tran sition to the configuration with lower energy E pot (i.e., the configuration more favorable energetically) and decreases opposite. We previously successfully applied this procedure when studying the evolution of tetrahe drane C 4 H 4 [25], cubane C 8 H 8 [26], and covalent complexes based on it [27,28].…”

Nonorthogonal tight-binding model for hydrocarbons

“…This makes possible the molecular dynamics simulations of relatively large systems for which ab initio calculations are problematic due to the limited computer power. Besides, the evolution of small clusters can be followed on a microsecond time scale [48,49] (the characteristic times are about 1-10 ps for ab initio molecular dinamics). On the other hand, this tight-binding potential fails to describe the tetrahedral hydrogen interstitial in diamond, although the bondcentred and hexagonal interstitials are well reproduced.…”

Nonorthogonal tight-binding model with H–C–N–O parameterisation

“…Earlier, we successfully used the nonorthogonal tightbinding model for hydrocarbons [20] to study the energy, structural, electronic and kinetic characteristics of a wide class of hydrocarbon systems, such as cubane [21] and its derivatives, [22 -24] graphane nanoribbons [25] and carbon peapods. [26] The results obtained are in good agreement with published experimental data and first principles calculations.…”