Ab Initio Molecular Dynamics Simulations of an Excited State of X^-(H₂O)₃(X = Cl, I) Complex

Abstract

Upon excitation of Cl(-)(H(2)O)(3) and I(-)(H(2)O)(3) clusters, the electron transfers from the anionic precursor to the solvent, and then the excess electron is stabilized by polar solvent molecules. This process has been investigated using ab initio molecular dynamics (AIMD) simulations of excited states of Cl(-)(H(2)O)(3) and I(-)(H(2)O)(3) clusters. The AIMD simulation results of Cl(-)(H(2)O)(3) and I(-)(H(2)O)(3) are compared, and they are found to be similar. Because the role of the halogen atom in the photoexcitation mechanism is controversial, we also carried out AIMD simulations for the ground-state bare excess electron -- water trimer [e(-)(H(2)O)(3)] at 300 K, the results of which are similar to those for the excited state of X(-)(H(2)O)(3) with zero kinetic energy at the initial excitation. This indicates that the rearrangement of the complex is closely related to that of e(-)(H(2)O)(3), whereas the role of the halide anion is not as important.

Direct dynamics simulations of photoexcited charge-transfer-to-solvent states of the I−(H2O) (n= 4, 5 and 6) clusters

“…Notice that the cyclic structure of water network finally converted into a linear chain structure at t $ 1500 fs. This process is quite similar to the results of Timerghazin and Peslherbe [18] and of Kołaski et al [19]. However, a completely different dynamics was obtained for the iodide atom motion.…”

“…Timerghazin and Peslherbe [18] have found that the heavy iodide atom was slowly departing from the ðH 2 OÞ À 3 anion cluster although the energy partitioned into the iodide kinetic energy was found to be very small ($0.01 eV). Kołaski et al [19] also found the iodide detachment dynamics in their simulation, where the kinetic energy of the I atom were estimated to be 0.03-0.04 eV. On the other hand, in our BOMD simulation, the iodide atom does not detach from the water cluster but is finally bound to the terminal water molecule in the linear chain ðH 2 OÞ À 4 cluster.…”

“…We set the initial kinetic energies of the system to zero. This is a somewhat unrealistic condition although the previous dynamics simulations for the I À (H 2 O) n cluster [18,19] have also been made with zero kinetic energy. It is possible to apply finite kinetic energy (finite cluster temperature); however, it may be difficult to choose appropriate initial conditions.…”

“…Recently, Timerghazin and Peslherbe [18] and Kołaski et al [19] have independently performed trajectory simulations after CTTS photoexcitation to the excited-state potential energy surface using a direct dynamics computational technique. These two groups have employed the complete-active-space self-consistent (CASSn = 4 n = 5 n = 6 [20].…”

Understanding Clusters toward the Design of Functional Molecules and Nanomaterials

“…11). 191 Similarly, one can utilize electric fields to control conformational changes of molecular clusters. Using ab initio study, we investigated geometries, energies, dipole moments, and transition states of the most stable cyclic water clusters with the increasing strength of electric field.…”