Analytical potential energy surfaces for N3 low-lying doublet states

Abstract

Adiabatic potential energy surfaces (PESs) for five low lying doublet states (three (2)A(') states and two (2)A(") states) of N(3) are constructed based on 1504 single point calculations at the MRCISD(Q) level using aug-cc-pVTZ basis set. A new strategy is adopted to obtain the final PESs by combining global fits of individual adiabatic PESs and local simultaneous fits of two adiabatic PESs in several conical intersection regions with switching functions. These global fits employ basis functions that satisfy permutational invariance with respect to like nuclei and have rms errors around 2-3 kcal/mol. The special local two-state fits are performed at the cyclic, bent, and linear N(3) conical intersection regions to take account of intrinsic square root behavior of the potentials and to improve the quality of fitting. Stationary points as well as minima on the concial intersections and seams of crossing are located on these PESs and compared with ab initio results. The agreement is satisfactory in most cases. In addition to the construction of adiabatic PESs, diabatization is performed for the 1 (2)A(') and 2 (2)A(') states around their conical intersection at the N(3) bent region. These two diabatic PESs and the diabatic coupling potential have been constructed and reported.

On the representation of coupled adiabatic potential energy surfaces using quasi-diabatic Hamiltonians: A distributed origins expansion approach

“…[1][2][3] Efforts to find diabatic representations include the vibronic coupling model of Köppel, Domcke, and Cederbaum; 4-12 the perturbation theory based work of Mead, Truhlar, and Varandas; 13, 14 the direct diabatization schemes of Truhlar, 15,16 based on earlier work of Ruedenberg; 17 the regularized diabatization procedure of Köppel; 18 the block diabatization method of Pacher,Cederbaum,and Köppel;19,20 the Shepard interpolation based method of Collins, Evenhuis, and coworkers; [21][22][23] and methods specific to triatomic molecules with nontrivial point group symmetry. 24,25 Approaches based on a combination of the interpolated moving least squares 26,27 and the general dynamically weighted 28 state averaged multia) E-mail: virtualzx@jhu.edu. b) E-mail: yarkony@jhu.edu.…”

Exploring Multiple Potential Energy Surfaces: Photochemistry of Small Carbonyl Compounds

“…In constructing an analytical PES, prior knowledge about the mechanisms obtained by the present approach will be very useful for effective sampling of the PES data with the least number of ab initio calculations, avoiding exhaustive sampling on a perfect grid covering all configurations. One technical but significant issue in this approach is how to represent the square root topology of conical intersections, and several approaches have been proposed [147][148][149][150].…”

N(4S /2D)+N2: Accurate ab initio-based DMBE potential energy surfaces and surface-hopping dynamics

“…Table II gives a comparison between the stationary structures of the DMBE PES and the ones obtained in Ref. 36, where the present fit is shown to accurately mimic the ab initio data, even for the position and energy of the minimum on the crossing seam. As seen in Table II, there is one stationary structure (TS up ) found in this work for the upper sheet that, to the best of our knowledge, has not been reported before (perhaps due to its asymmetric C s nature).…”

“…The PESs of the azide radical have been much studied by Morokuma and co-workers, [34][35][36] and previously by other groups, [37][38][39][40][41] for geometry optimizations, fundamental frequencies, dipole moments, minima on the seam of crossings (MSX), and vertical excitations. A brief survey of such attributes is given here, while presenting our previous PESs as modelled via double many-body expansion (DMBE (Refs.…”

“…The MRCI(Q)/AVTZ prediction34,36 for the minima on the seam of different types of crossings is indicated with the symbols.…”