Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session R03: Challenges for Excited States and Dynamics IFocus

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Sponsoring Units: DCP DCOMP Chair: Laura Gagliardi, University of Minnesota Room: LACC 150C 
Thursday, March 8, 2018 8:00AM  8:36AM 
R03.00001: Challenges for excited states and dynamics in the presence of environment Invited Speaker: Leticia Gonzalez The accurate description of excited states and its dynamics of molecules in the presence of an environment is a very challenging task because it requires, at least i) an appropriate description of the interactions between the chromophore and the environment, and ii) the calculation of the vibrational motion of the whole system. For the former, it is common to describe the environment either by quantum mechanics/continuum or quantum mechanics/molecular mechanics models. For the second, vibrational sampling can be described with Wigner sampling or with molecular dynamics. Several examples will be first shown to illustrate how different models can dramatically affect the excited states energies and other properties of the molecule. In the case of flexible molecules and in order to perform nonadiabatic dynamics, the situation is even more complex, as Wigner distributions cannot be used as initial conditions and molecular dynamics is not suitable to describe large amplitude motions correctly. Surfacehopping simulations using our local code SHARC for nonadiabatic dynamics including spinorbit couplings will be shown on a transition metal complex in solution. 
Thursday, March 8, 2018 8:36AM  8:48AM 
R03.00002: DualFunctional TammDancoff Approximation: A Convenient Density Functional Method that Correctly Describes S_{1}/S_{0} Conical Intersections. Yinan Shu, Kelsey Parker, Donald Truhlar Accurate nonadiabatic dynamics simulations require sophisticated electronic structure theories that can describe the complex wavefunctionsin different regions of the potential energy surfaces (PESs). Conical intersections (CIs), facilitating the population transfer from one state to the other, play an important role in the nonadiabatic processes. Hence, efficient and accurate electronic structure theories should correctly describe the double cone topology of the PESs near CI. The current theories that can correctly describe the CI regions of the PESs are mostly based on the multireference methods. However, the computational cost of the multireference methods grows exponentially when the active space increases. On the other hand, LRTDDFT is both efficient and accurate but unable to describe the CIs between ground and excited states. Hence the applications of LRTDDFT in the nonadiabatic processes are limited. In this presentation, we introduce a novel theoretical method based on LRTDDFT, named dual functional TammDancoff approximation that can describe the correct topology of the PESs near CI and can be accurate as LRTDDFT. 
Thursday, March 8, 2018 8:48AM  9:00AM 
R03.00003: Quasi Diabatic Representation for Nonadiabatic Quantum Dynamics Propagations Pengfei Huo We develop a nonadiabatic quantum dynamics propagation scheme that allows interfacing diabatic quantum dynamics approaches with routine adiabatic electronic structure calculations. This new scheme is based a quasidiabatic (QD) representation that uses adiabatic states as diabatic states during a shorttime quantum dynamics propagation. Between two consecutive shorttime propagations, the electronic state basis is transformed from the old to the new QD representation. This scheme allows using diabatic quantum dynamics method with any adiabatic electronic structure methods, resolving the incompatibility challenge between the two methods due to their different representations. In addition, with the QD scheme one avoids explicitly computing the derivative coupling vectors and thus alleviate the numerical instability for quantum propagations in the cases where these vectors change rapidly in time. Using a recently developed diabatic quantum dynamics approach, Partial Linearized Density Matrix (PLDM) pathintegral method as a specific exampel, we have demonstrated the accuracy of this QD scheme with a wide range of model nonadiabatic problems as well as the onthefly propagations with Density Functional TightBinding (DFTB) calculations. 
Thursday, March 8, 2018 9:00AM  9:12AM 
R03.00004: SpinForbidden Channels in the Reactions of Unsaturated Hydrocarbons and O(^{3}P) Pavel Pokhilko, Anna Krylov A number of theoretical and experimental studies indicate that the role of spinforbidden channels in the reaction of unsaturated hydrocarbons and O(^{3}P) can be important. Branching ratios of the products are sensitive to the chemical structures of the reactants. In our study we use equationofmotion coupledcluster methods to investigate electronic structure and to predict the difference in branching ratios for ethylene, propylene, and acetylene. To evaluate one and twoelectron spinorbit matrix elements we use perturbative approach. All matrix elements are obtained by rotation of the molecules and applying the corresponding Wigner matrices. 
Thursday, March 8, 2018 9:12AM  9:48AM 
R03.00005: Optimized Ensemble TimeDependent Density Functional Theory Invited Speaker: Filipp Furche The recent discovery of unphysical divergences in approximate 
Thursday, March 8, 2018 9:48AM  10:00AM 
R03.00006: Nonadiabatic molecular dynamics of carbon dioxide at metal surfaces Philip Shushkov, Yunxi Yao, konstantinos giapis, Thomas Miller We investigate theoretically the collisions of carbon dioxide with gold surfaces at hyperthermal kinetic energies. We parameterize an accurate and computationally efficient systemspecific tightbinding model to propagate molecular dynamics trajectories and sample over initial conditions, and incorporate the electronhole pair excitations in the metal by an electronic friction model. We observe that the molecular electronic states interact along the trajectories of atomic motion and describe the nonadiabatic coupling at the stateaveraged complete active space selfconsistent field level. The theoretical model allows us to gain insight into the nonadiabatic molecular dynamics of carbon dioxide at metal surfaces. 
Thursday, March 8, 2018 10:00AM  10:12AM 
R03.00007: On the exact factorization equations and quantumclassical approximations Graeme Gossel, Federica Agostini, Neepa Maitra A timedependent molecular wavefunction may be written exactly as a single product of the nuclear and electronic wavefunctions, with a pair of corresponding equations of motion [1]. Although the nuclear equation is a timedependent SchrÃ¶dinger equation, the electronic equation is not and has a structure with as yet unknown stability and convergence properties. We present preliminary studies of this, with a view to investigating approximations to the nonadiabatic terms. 
Thursday, March 8, 2018 10:12AM  10:24AM 
R03.00008: Photodissociation dynamics of organic iodides studied via ultrafast photoelectron spectroscopy Brian Stankus, Nikola Zotev, David Rodgers, Yan Gao, Adam Kirrander, Peter Weber Photodissociation reactions are prototypical systems for ultrafast dynamics studies. While direct excitation to a repulsive excited state followed by direct dissociation is the fastest dissociation mechanism, bond breaking can occur via a variety of pathways. In the present study, we use ultrafast photoelectron spectroscopy with resonant ionization via molecular Rydberg states to investigate CI bond cleavage in the molecule 1,4diiodobenzene excited by 4.6 eV photons. The photoelectron spectrum suggests that the first step of the dissociation is an ultrafast curve crossing from the initially excited bound state. Subsequent probing via resonant ionization reveals a detailed picture of the ensuing wavepacket dynamics. 
Thursday, March 8, 2018 10:24AM  11:00AM 
R03.00009: NonAdabatic Chemiluminescent Dynamics of the MethylSubstituted 1,2Dioxetanes Invited Speaker: Roland Lindh

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