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We calculate the adiabatic potential energy surfaces (PESs) and the non-adiabatic coupling terms (NACTs) for the excited electronic states of K 3 cluster by MRCI approach using MOLPRO. The NACTs are adapted with molecular symmetry to assign appropriate IREPs so that the elements of the Hamiltonian matrix are totally symmetric. We incorporate those NACTs into three-state adiabatic-to-diabatic transformation (ADT) equations to obtain ADT angles for constructing continuous, single-valued, smooth and symmetric diabatic Hamiltonian matrix, where its elements are fitted with analytic functions. Finally, we demonstrate that the dressed diabatic and adiabatic-via-dressed diabatic PECs show prominent topological effect over dressed adiabatic curves. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract A five-state multimode non-adiabatic dynamics has been performed on NO 3 by constructing accurate diabatic potential energy surfaces (PESs) in vibronically coupled manifold using beyond Born-Oppenheimer (BBO) theory. In this article, we have considered the photodetachment of NO 3 - to the doublet states ( X ∼ 2 A 2 ′ , A ∼ 2 E ″ and B ∼ 2 E ′ ) of NO 3 and determined the vibronic couplings and conical intersections of the latter. Using ab initio calculated adiabatic PESs and Non-adiabatic Coupling Terms, we have carried out adiabatic-to-diabatic transformation (ADT) in five-state sub-Hilbert space to obtain ADT angles and thereby, constructed single-valued, smooth, symmetric and continuous diabatic PESs. The explicit analytic expressions for diabatic PESs and coupling elements are provided. Subsequently, we have performed nuclear dynamics starting from the electronic ground state of NO 3 - to simulate photodetachment spectra. The overall spectral profiles for 2 A 2 ′ and 2 E ″ states show reasonably good agreement with experimental results and that of 2 E ′ state with other theoretical calculations. [ABSTRACT FROM AUTHOR]

[Display omitted] We employ trajectory surface hopping (TSH) formalism [Chem. Phys. 349 (2008) 334, J. Chem. Phys. 142 (2015) 144307] to compute cross-sections or/and rate constants of D+ + H 2 (v = 0 , j = 0) and H + H 2 + (v = 0 , j = 0) reactions initiating from ground and first excited electronic state of H 3 + , respectively. While solving Hamilton's equations over adiabatic potential energy surfaces (PESs), switching probabilities are calculated by ab initio nonadiabatic coupling terms for the first time. During hopping, momenta are adjusted to fulfil total energy conservation, where a scaling factor is introduced to explore the conservation of linear momentum. For non-charge transfer process, quasi-classical cross-sections match well with quantum results obtained from diabatic PESs of H 3 + and experimental findings, but deviations are observed at the energy domain of conical intersection driven hopping for charge-transfer processes. Calculated results indicate the origin of limitations of TSH algorithm as well as depict computational advantage with respect to quantum dynamics. [ABSTRACT FROM AUTHOR]

Abstract: We explore both the general symmetry-allowed accidental (SAA) conical intersections (CIs) and Renner–Teller (RT) interactions prevailed between the ground ( ) and first excited ( ) electronic states of in the configuration space of normal mode coordinates. Global ab initio potential-energy surfaces and Non Adiabatic Coupling Term (NACT) between those states are reported. For each of the three pairs of normal mode ( ), calculated NACT show singularity at different positions, which are used to calculate Adiabatic-to-Diabatic Transformation (ADT) angles and thereby, the diagonal elements of ADT matrix display (i) sign change for odd number of SAA CI (s) and (ii) no sign change for even number of SAA CIs as well as Renner–Teller interactions. Similar to Jahn–Teller CI, the existence of SAA CIs are, further, confirmed by Longuet-Higgins’ phase change. [Copyright &y& Elsevier]