New Double Many-Body Expansion Potential Energy Surface for Ground-State HCN from a Multiproperty Fit to Accurate ab Initio Energies and Rovibrational Calculations

Abstract

An accurate single-sheeted double many-body expansion potential energy surface has been obtained for the ground electronic state of the hydrogen cyanide molecule via a multiproperty fit to ab initio energies and rovibrational data. This includes 106 rovibrational levels and 2313 discrete points, which are fit with a rmsd of 4 cm(-1) and 2.42 kcal mol(-1), respectively, and seven zero first-derivatives that are reproduced at three stationary points. Since the potential also describes accurately the appropriate asymptotic limits at the various dissociation channels, it is commended both for the simulation of rovibrational spectra and reaction dynamics.

Accurate Double Many-Body Expansion Potential Energy Surface for the Lowest Singlet State of Methylene

“…The three-body switching function assumes the form expressions applying for f j and f k . Following a recent proposal 41 to correct the long-range behavior, we adopt η ) 6 and to be equal to 1.0a 0 -1…”

HN2(2A‘) Electronic Manifold. II. Ab Initio Based Double-Sheeted DMBE Potential Energy Surface via a Global Diabatization Angle

“…Following recent work on HCN 81 we have fixed η ) 6 and ) 1.0a 0 -1 . The damping function n (r i ) was the same as for the diatomics, but using the center-of-mass separation for the relevant atom-diatom channel instead of R. The parameter F for both diagonal diabatic states was the one used for the single-sheeted potential energy surface of HN 2 -( 2 A′), 2 were R 0 was taken as the average of the corresponding parameters for NO and SiH, which leads to F ) 15.9.…”

Accurate DMBE Potential Energy Surface For the N(2D) + H2(1Σ g + ) Reaction Using an Improved Switching Function Formalism

“…Following recent work on HCN [34], we have fixed η = 6 and ξ = 1.0 a 0 −1 . Regarding, the damping function χ n (r i ), we still adopt [31] Eq.…”

“…To correct such a behavior, we have multiplied the two-body dynamical correlation energy for the ith pair by j =i 1 − f j (correspondingly for channels j and k). This ensures [31,34] that the only two-body contribution at the ith channel is that of JK.…”