First-principles study on the infrared spectra of ice nanotubes

The structures and infrared (IR) spectra of ice nanotubes (INTs) are studied by the density functional theory and density functional perturbation theory in the generalized gradient approximation. Applying the group theory, we analyze the vibrational properties of the IR-active modes in the connectivity, librational, bending, intra-ring OH stretching, and inter-ring OH stretching regions. The origins of the IR-active modes are systematically investigated. Our calculation shows that the unusual form of hydrogen bonds in the INTs plays an important role in the signatures of their IR spectra, especially in the inter-ring OH stretching region, whose frequencies are significantly higher than those in ice-Ih case; Our result is in good agreement with an available experimental and theoretical report.

Graphical AbstractThe higher-frequency modes at 3540–3550 cm−1 are associated with the weaker inter-ring H-bonds. Our calculations are very close to the experimental value of 3507 cm−1, and also consistent with the previous DFT and DFPT result 3555 cm−1 as well as the classical MD result 3517 cm−1, but remarkably differs from the SCC-DFTB-D result (∼3700 cm−1).Figure optionsDownload as PowerPoint slideHighlights
► Structures and infrared (IR) spectra of ice nanotubes (INTs) studied by the density functional theory and density functional perturbation theory in the generalized gradient approximation.
► Applying the group theory, the vibrational properties of the IR-active modes in “connectivity”, librational, bending, intra-ring OH stretching, and inter-ring OH stretching regions are analyzed.
► Origins of the IR-active modes are systematically investigated.
► Our calculation shows that the unusual form of hydrogen bonds in the INTs plays an important role in the signatures of their IR spectra, especially in the inter-ring OH stretching region, whose frequencies are significantly higher than those in ice-Ih case.
► Our result is in good agreement with an available experimental and theoretical report.