Supercollisions of fast H-atom with ethylene on an accurate full-dimensional potential energy surface

Abstract

The collisions transferring large portions of energy are often called supercollisions. In the H + C2H2 reactive system, the rovibrationally cold C2H2 molecule can be activated with substantial internal excitations by its collision with a translationally hot H atom. It is interesting to investigate the mechanisms of collisional energy transfer in other important reactions of H with hydrocarbons. Here, an accurate, global, full-dimensional potential energy surface (PES) of H + C2H4 was constructed by the fundamental invariant neural network fitting based on roughly 100 000 UCCSD(T)-F12a/aug-cc-pVTZ data points. Extensive quasi-classical trajectory calculations were carried out on the full-dimensional PES to investigate the energy transfer process in collisions of the translationally hot H atoms with C2H4 in a wide range of collision energies. The computed function of the energy-transfer probability is not a simple exponential decay function but exhibits large magnitudes in the region of a large amount of energy transfer, indicating the signature of supercollisions. The supercollisions among non-complex-forming nonreactive (prompt) trajectories are frustrated complex-forming processes in which the incoming H atom penetrates into C2H4 with a small C–H distance but promptly and directly leaves C2H4. The complex-forming supercollisions, in which either the attacking H atom leaves (complex-forming nonreactive collisions) or one of the original H atoms of C2H4 leaves (complex-forming reactive trajectories), dominate large energy transfer from the translational energy to internal excitation of molecule. The current work sheds valuable light on the energy transfer of this important reaction in the combustion and may motivate related experimental investigations.

Unexpected steric hindrance failure in the gas phase F− + (CH3)3CI SN2 reaction

“…The current 39-dimensional PES of the title reaction was developed by the recently proposed fundamental invariant neural network (FI-NN) 37 – 41 approach. Due to the huge computational cost of the gold standard coupled-cluster calculations for this 15-atom system with six heavy atoms, we employed the CAM-XYG3/AVTZ(AVTZ-PP for iodine atom) 42 , 43 method alternatively, which archives a similar level of accuracy as compared to CCSD(T)/AVTZ(-PP) but significantly reduces the computational effort.…”

A highly accurate full-dimensional ab initio potential surface for the rearrangement of methylhydroxycarbene (H3C–C–OH)

“…59,60 In contrast to the PIP-NN method, the current FI-NN minimizes the size of input invariants which consist of the least number of invariants at a specific truncated or maximum degree. The FI-NN method has been widely used to construct the PESs and the details of the FI-NN method have been extensively listed in the earlier work of our group 48,51,61 or others. [62][63][64] To balance the calculation accuracy and PES fitting time, we used 222 FIs with a specific maximum order of 5 as the input vector of the NN.…”

Infrared spectroscopy and theoretical structure analyses of protonated fluoroalcohol clusters: the impact of fluorination on the hydrogen bond networks

“…In n = 3, which is the minimum size to form a H-bonded ring, the OHÁ Á ÁO angle is largely deviated from the optimized angle (1801) for a H-bond. [33][34][35][36][37][38][39][40][41][42] Because of the large stress of the H-bonds in the neat H-bonded ring of n = 3, the non-cyclic structure involving OHÁ Á ÁFC interactions can be more stable. Such a case has been reported for FE.…”

“…H-Bonded structures of small neutral clusters of TFE, 2-fluoroethanol (FE), and 1,1,1,3,3,3-hexafluoropropan-2-ol have been studied by microwave and IR spectroscopy with theoretical computations. [28][29][30][31][32] While neutral (ROH) n generally forms H-bonded cyclic structures in n Z 3, [33][34][35][36][37][38][39][40][41][42][43] the OHÁ Á ÁO H-bonded network is open in (FE) 3 and an OHÁ Á ÁFC H-bond is involved to keep a cyclic structure of the cluster. 28 Also in (TFE) 3 , such a cyclic structure involving an OHÁ Á ÁFC bond competes with the neat OHÁ Á ÁO H-bonded cyclic structure.…”

“…Moreover, in the neutral alcohol clusters, the possible change of the H-bonded network structure is limited only to cyclic/linear conversion. [33][34][35][36][37][38][39][40][41][42][43] In protonated alcohol clusters, the size-selection can be freely performed by the mass spectrometric techniques to explore larger sized clusters. The multi-step development of the H-bonded network structures has been known for the protonated alcohols, and the influence of the fluorination would be easily found by the comparison with the previously studied protonated alcohols.…”