Effect of confinement of water monomer and dimer under confined geometries of carbon nanostructures

In the present study, we have confined the smallest water clusters namely, monomer and dimer under various carbon nanotubes and fullerenes using quantum mechanics/molecular mechanics methods. We observed the change in their structural, vibrational, optical and electronic properties as compared to each other as well as against the free monomer and dimer. For monomer, the confinement effect was found to be the greatest for carbon nanotube CNT(7,0) followed by C-60 and then by C-78. However, in the case of the dimer, there was a change in its structure, thus exhibiting different confining effects in each geometry. We also note that, as the diameter of the CNT goes on increasing, the confining effects over the monomer and the dimer go on decreasing. We have also confined a monomer by placing it over one C-60 fullerene, and between two and three C-60 fullerenes at various sites-the hexagon, pentagon and the vertex at different distances from the surface, and compared the extent of confinement. In the vibrational spectra, for short-range interactions, a redshift was observed, whereas a blueshift was seen in the case of long-range interactions as we went from hexagon to pentagon to vertex sites. We have also confirmed the results obtained by studying their structural, vibrational, electronic and optical properties.