Theoretical study of the anthropogenic greenhouse gas (SF₅CF₃) and analysis of the reaction of SF₆ with CF

Abstract

SF 5 CF 3 was recently detected in the earth's atmosphere. This has lead to various experimental and theoretical studies aimed at establishing the properties of this molecule, from which to understand how it is formed, how it may impact on the atmosphere (it is a powerful greenhouse gas), and how it may be destroyed in the atmosphere. SF 5 CF 3 is chemically very inert, and is not destroyed in the troposhere. Theoretical calculations using effective core potential (ECP) based on high-level methods -QCISD(T), were performed for molecular systems related to SF 5 CF 3 . Existing values for the S-C bond dissociation energy in SF 5 CF 3 span a wide range, from estimates of about 200 to 300 kJ mol −1 , obtained from theoretical calculations on SF 5 CF 3 using the DFT, G2, and G3 protocols, to 390 ± 45 kJ mol −1 derived from experimental studies of the photoionisation of SF 5 CF 3 . At the QCISD(T)/ECP+GCM (generator coordinate method) level, the dissociation energy -D o (SF 5 -CF 3 , 0 K), is 274.7 kJ mol −1 . In addition to calculations on individual molecules, the reactions of SF 6 with CF − 3 were studied. The first objective was to locate the reactant ion-molecule complex, the transition state, and the product ion-molecule complex for each of these systems. On the basis of literature thermochemistry, the reaction of SF 6 with CF

Composite Method Employing Pseudopotential at CCSD(T) Level

“…The GCM has been very useful in the study of basis sets (Morgon, 1995a;2006;2008b;2011;Morgon et al, 1997). It considers the monoelectronic functions ψ(1) as an integral transform,…”