> For the complete documentation index, see [llms.txt](https://docs.materialsproject.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.materialsproject.org/methodology/molecules-methodology/vibrational-properties.md).

# Vibrational Properties

DFT vibrational frequency analyses produce a set of frequencies, their predicted spectroscopic activities and intensities, and the vibrational normal modes associated with each frequency. From these individual components, we report predicted infrared spectra.

In DFT, the reported frequencies are reported as single numerical values, leading to IR spectra with infinitely thin peaks (so-called "stick spectra"). On the Materials Project Web site, we allow users to visualize the computed IR spectra with broadened peaks based on Gaussian and Lorentzian lineshapes.