JPCA: accurate and affordable IR spectra with AIQM

Recently, we cooperated with Xiamen University and published a paper in JPCA about how to do accurate and fast IR spectra simulations with AIQM models.

Specifically, it is about the accurate and affordable simulation of gas-phase infrared spectra with AIQM models. By comparing to more than 7000 experimental spectra, we found that AIQM models are much faster than DFT while achieving comparable accuracy.

Theoretical IR (infrared) spectroscopy is a powerful tool for assisting chemical structure identification. However, approaches based on quantum chemical calculations suffer from either high computational cost (e.g., density functional theory) or insufficient accuracy (semi-empirical methods).

Hence, we introduce a new approach based on the universal machine learning models of AIQM series.

AIQM methods, particularly, newly introduced AIQM2, can provide IR spectra with accuracy close to DFT and the speed close to a semi-empirical GFN2-xTB method.

To ensure high speed and interpretability, our implementation is based on the harmonic approximation with the frequencies scaled by factors that we found empirically.

You can easily do such calculations yourself using MLatom, which comes with tutorials and example scripts.

You can even do the IR spectra simulation now online, on the Aitomistic hub. Opening your molecule visualizing it and then clicking on this infrared button, and then it will automatically do the AIQM2 calculations.

Here it shows the summary of calculations, which include the frequencies and intensities in raw format.

As you see, you can start from any geometry, even this ridiculously linear ethanol molecule, and then it will optimize the geometry with AIQM2 and do frequency calculations and produce here on the right infrared spectrum.

You can also attribute normal mode vibrations to specific bands in the infrared spectrum in the Jupyter Lab on the same website.

And, nowadays you can also do the simulations using Aitomia intelligent assistant. On the hub you can chat with it. Here's an example doing the same thing but for hexanol molecule by chatting in Aitomistic Hub. Aitomia produces a spectrum for hexanol with pretty decent accuracy compared to experiments.

If you have any questions about how to run these calculations, you can check our tutorials, the paper, and also chat with us online on Slack.