Frequency and IR Calculation
Overview
Frequency and IR calculations compute the vibrational frequencies and infrared (IR) spectra of molecules at their optimized or given geometries. These calculations provide insights into molecular vibrations, thermodynamic properties, and help identify characteristic functional groups through IR spectroscopy analysis. Check the Input and Visualizer section for the allowed input types and how to upload the files.
Note
Frequency calculations require the molecular geometry to be at a stationary point (preferably an optimized geometry) for meaningful results.
Hybrid ML Module Input Fields
Upon selecting the Hybrid ML module, following inputs have to be provided:
Total charge of the molecule (e.g., 0)
Spin mulitplicity = 2S+1 (e.g., 1 for singlet)
GFN2-XTB Module Input Fields
If the GFN2-XTB module is selected, the following inputs must be provided:
Total charge of the molecule (e.g., 0)
Spin multiplicity = 2S+1 (e.g., 1 for singlet)
Toggle to include solvent effects
Select a solvent (e.g., water, ethanol)
DFT Module Input Fields
Upon selecting the DFT module for frequency calculations, the following inputs must be provided:
Total charge of the molecule (e.g., 0)
Spin multiplicity = 2S+1 (e.g., 1 for singlet)
Select the basis set family (e.g., Pople, Dunning)
Select the basis set (e.g., def2-tzvpp, 6-31G*)
Choose an exchange-correlation functional (e.g., B3LYP)
Toggle to enable IR spectrum calculation and normal mode analysis.
Note
We have LDA, PBE, PBE0, M06, B3LYP, CAM-B3LYP and WB97X functionals available right now for the GPU calculations.
Note
When Calculate IR is enabled, the calculation will compute normal modes. Finally, click the Run Calculation button to start the simulation.
Output Details
The following options are available to explore and save the results of your frequency calculation:
View all task details including computational parameters units.
Complete list of calculated vibrational frequencies.
Interactive IR spectrum plot showing frequency vs. intensity for all IR-active vibrational modes.
3D visualization of vibrational normal modes when Calculate IR is enabled, allowing interactive exploration of molecular motions.
Download the complete output files including frequency data in csv format.
To visualise the normal modes, first enable the Structure View, then select the mode from the dropdown menu. You can play, pause, and adjust the speed of the animation.
Note
Imaginary Frequencies: If imaginary frequencies (negative values) are present, they indicate that the geometry is not at a true minimum on the potential energy surface. Consider performing geometry optimization first.
Tip
IR Analysis: Use the IR spectrum to identify characteristic functional group vibrations such as C-H stretches (~3000 cm⁻¹), C=O stretches (~1700 cm⁻¹), and fingerprint region vibrations (400-1500 cm⁻¹).
Note
Thermochemistry Properties Coming Soon: Detailed thermodynamic properties including entropy, enthalpy, and Gibbs free energy calculations are currently under development and will be available in an upcoming release.