Accurate potential energy surface of H2S+(X 2 A″) via extrapolation to the complete basis set limit and its use in dynamics study of S + ( D 2 ) + H 2 ( X 1 Σ g + ) reaction

A new global analytical ab initio potential energy surface for the dynamics of the C+(2P) + SH(X2Π) reaction

The global potential energy surface (PES) of HCS⁺(X¹Σ⁺) is constructed using many-body expansion (MBE) methodology. The obtained analytical function is found by fitting the 7907 ab initio energy points computed at the Davidson-corrected multi-reference configuration interaction level with the aug-cc-pV(5+d)Z basis set. The final root mean square error is 0.0419 eV, and the maximum deviation is 0.2039 eV, showing that the analytical formula agrees well with the energy points. The topological features are calculated and discussed based upon the analytical PES of HCS⁺(X¹Σ⁺). The reaction probability, integral cross sections and other details of the C⁺(²P) + SH(X²Π) → H(²S) + CS⁺(X²Σ⁺) reaction are investigated using the quasi-classical trajectory and time-dependent quantum wave packet methods.

A global CHIPR potential energy surface of PH2(X2B1) via extrapolation to the complete basis set limit and the dynamics of P(2D) + H2(X1Σ+g) → PH(X3Σ−) + H(2S)

A global PEC of the ground state PH2 was constructed using the CHIPR method based on accurate MRCI(Q)/CBS(T, Q) energy points. The ICS and k(T) of P(2D) + H2(X1Σ+g) → PH(X3Σ−) + H(2S) were calculated based on the QCT method.

Accurate Potential Energy Surface for Quartet State HN2 and Interplay of N(4S) + NH(X̃3Σ-) versus H + N2(A3Σu+) Reactions

A global potential energy surface for the lowest quartet state of HN₂ 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 HN₂ predicted to have a bent global minimum 36 kcal mol^-1 below the N(⁴S) + NH(X̃³Σ^-) 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.

Accurate global potential energy surface for SiH2 +(X2A1) and quantum dynamics of related reaction H(2S) + SiH+(X1Σ+)

With the many-body expansion method, an accurate global potential energy surface (PES) is constructed for SiH₂ ⁺(X²A₁) by mapping 4762 ab initio energy points calculated on the multireference configuration interaction level including Davidson corrections with aug-cc-pV6Z Dunning's basis set. The dissociation energies and equilibrium geometries of SiH⁺(X¹Σ⁺) and H₂(X¹Σ_g ⁺) agree well with the experimental results. The topographical characteristics of all stationary points for the SiH₂ ⁺(X²A₁) PES are discussed in detail and compared with other theoretical and experimental results. In order to verify the validity and usability of the present PES, the dynamics calculations based on the Chebyshev quantum wave packet method are performed for the H(S2)+SiH⁺(X¹Σ⁺)→Si⁺(P2)+H₂(X¹Σ_g ⁺) reaction. The probabilities, the total integral cross sections, and the rate constants are computed, and the analogies with the corresponding ones of reaction H(S2) + CH⁺(X¹Σ⁺)→C⁺(P2) + H₂(X¹Σ_g ⁺) are also made. The reasonable dynamical behavior throughout the entire configuration space indicates that the PES is suitable for relevant dynamics investigations and serves as a building block for constructing the PES of larger molecular systems containing Si⁺/H.