Accurate Potential Energy Surface for Quartet State HN₂ and Interplay of N(⁴S) + NH(X̃³Σ^–) versus H + N₂(A³Σ_u⁺) Reactions

Abstract

A global potential energy surface for the lowest quartet state of HN 2 is reported for the first time from accurate multireference ab initio calculations extrapolated to the complete basis set limit using the double many-body expansion method. All its stationary points are characterized, with the lowest quartet of HN 2 predicted to have a bent global minimum 36 kcal mol −1 below the N( 4 S) + NH(X ̃3Σ − ) asymptote, from which it is barrierlessly achievable. The entire set of calculated ab initio points has been fitted for energies up to 1000 kcal mol −1 above the global minimum with an RMSD of 0.89 kcal mol −1 , a gap comprising all identified stationary points. Special care is taken in modeling the involved long-range forces and cusps caused by crossing seams. The novel PES prompts for the calculation of rate constants for several unexplored reactions that are relevant for combustion, plasma, and atmospheric chemistry.

Self-consistent modeling of microwave activated N2/CH4/H2 (and N2/H2) plasmas relevant to diamond chemical vapor deposition

“…What is clear, however, is that these recent calculations [32] overestimate k 19 (T g ) at low temperatures, since the reported k 19 (298 K) value is some two orders of magnitude larger than the value (2.8 × 10 −15 cm 3 s −1 ) used to accommodate the data of Hack et al [58]. Mota et al [33] predict a barrier in the entrance channel to reaction (19). Adopting the k 19 (2000 K) value from [32] and the above value of k 19 (298 K) leads to the k 19 (T g ) expression listed in table 1, with an activation energy of 2721 K (0.235 eV) somewhat larger than the reaction endothermicity (∼0.18 eV).…”

“…Apart from the important reactions ( 27)-(31) discussed above, other possible radical reactions (32) and (33) only make small additional contributions to the overall loss of NHx species, as can be seen from Table 2. Loss of N atoms and other NHx radicals at the substrate surface (with probabilities near (or lower than) those prevailing in an N/H plasma discussed above) is insignificant in comparison with loss by gas phase reactions with CxHy radicals (Table 2).…”

“…Recent calculations for the reaction of metastable N 2 molecules with H atoms (i.e. the N 2 (A 3 Σ + u ) + H → NH + N reaction) [32,33] and for the quenching of N 2 (A 3 Σ + u ) molecules by H 2 [34], along with more detailed N/C/H plasma-chemical kinetics involving higher excited states of N 2 , allow some refinement of this issue. Third, the debate concerning the more important gas phase source(s) of potentially active nitrogen (e.g.…”

The P(4S) + NH(3Σ–) and N(4S) + PH(3Σ–)reactions as sources of interstellar phosphorus nitride

“…However the latter is more than two times more exothermic, owing to the strong triple bond present in N 2 . Another striking difference is the presence of two deep minima in the HPN potential energy surface, while HN 2 only displays a shallow metastable minimum which lies higher in energy than the H + N 2 limit (Walch, Duchovic and Rohlfing, 1989;Mota & Varandas, 2007Mota, Galvão, Coura and Varandas, 2020). The presence of such minima will change the dynamics of the phosphorus reactions by allowing energy randomisation among the degrees of freedom during the complex lifetime, which will change the products distributions (Miller, Safron and Herschbach, 1967).…”

A comparative review of 50 analytical representation of potential energy interaction for diatomic systems: 100 years of history

“…The EHFACE2U potential energy curve is considered one of the best and more accurate functions to describe diatomic interactions, it is still widely used in recent researches [168–170]. In a recent work presented by da Silva and Ballester [171] the diatomic potential energy curves for triplet electronic states, X 3 ∑ − and B 3 ∑ − of SO has been described using the approach proposed by Varandas and da Silva [167].…”