Zongrong Xu

Temple University, Filadelfia, Pennsylvania, United States

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Publications (2)2.69 Total impact

  • ZongRong Xu · Spiridoula Matsika
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    ABSTRACT: A combined quantum mechanics/molecular mechanics method is described here for considering the solvatochromic shift of excited states in solution. The quantum mechanical solute is described using high level multireference configuration interaction methods (MRCI), while molecular dynamics is used for obtaining the structure of the solvent around the solute. The electrostatic effect of the solvent is included in the quantum description of the solute in an averaged way. This method is used to study solvent effects on the n(O) --> pi* electronic transition of formaldehyde in aqueous solution. The effects of solute polarization, basis sets, and dynamical correlation on the solvatochromic shift, and on dipole moments, have been investigated.
    No preview · Article · Nov 2006 · The Journal of Physical Chemistry A
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    ABSTRACT: Nonadiabatic processes play an important role on the excited state dynamics of chemical systems. Conical intersections (actual potential energy surface crossings) of two states have been established to facilitate nonadiabatic processes of molecules and radicals in the gas phase. More recently three-state conical intersections have made their appearance and may also play a key role in nonadiabatic processes. Here we present studies where the importance of conical intersections is being investigated in photoinitiated processes of biologically relevant systems, and particularly the nucleobases and their analogs. Large scale ab initio multireference configuration interaction methods (MRCI) are being used. Our results show the presence of many seams of two- or three-state conical intersections that can complicate the potential energy surfaces and dynamics of these systems. Solvent effects on conical intersections are first being investigated using clusters of water with the system. A mixed quantum mechanical/ classical mechanical (QM/MM) approach where the solute is described with the MRCI method will also be presented as a means to study the effect of the solvent on excited states.
    No preview · Article · Jan 2006