Laser-induced water decomposition near 2D sheets studied by TDDFT

In this presentation, we will show the TDDFT-Ehrenfest dynamics for pulse-laser induced decomposition of water molecules near 2D sheets, graphene, hBN and gC₃N₄. The assumed full-width of half-maximum (FWHM) of the field intensity spans from 10 fs to 20 fs, and the assumed wavelengths are 800nm and 400nm. We have found reduction of threshold intensity of optical E-field for the decomposition when water molecules are located near the 2D sheet. This fact is understood by optical field enhancement near the 2D sheet rather than their catalytic effect. The case with FWHM=20 fs gives smaller threshold intensity of the laser field than the case of FWHM=10 fs, yet the fluence per pulse is smaller with shorter FWHM. We further performed the simulation of several water molecules above graphene sheet keeping inter-water distances very close to those in bulk water. However, the threshold intensity for the water decomposition was less sensitive to the presence of the water-water interactions. The details of the present results was published in Phys. Rev. B96, 115451 (2017)