Applications of the Structure Search in Methanol Clusters: From Gas Phase to Liquid Phase

Po-Jen Hsu^3*, Soon Teh¹, Asuka Fujii², Jer-Lai Kuo³

¹Experimental Quantum Information Physics Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
²Department of Chemistry, Tohoku University, Sendai, Japan
³Institute of Atomic and Molecular Science, Academia Sinica, Taipei, Taiwan

* Presenter:Po-Jen Hsu, email:clusterga@gmail.com

H-bonded systems such as water or alcohol have drawn much attention in both experiments and theoretical calculations. Among them, methanol is often considered as one of the most fundamental H-bond systems compared to water and other alcohols due to the simplicity of its H-bond networks. Using IRPD, experimentalists are able to investigate the H-bond network of the protonated methanol in the gas phase. On the other hand, vibrational spectra of the liquid methanol can also be measured by the FTIR experiment. In this work, we start with extensively searched structure databases for protonated and neutral methanol clusters and computed the vibrational modes using density functional theory. To simulate the IR spectra, we adopted the quantum harmonic superposition approximation (Q-HSA) for the gas phase and the quantum cluster equilibrium (QCE) theory for the liquid phase. Moreover, we extend the structure database from methanol to tert-butanol, which allows us to examine the competition between the H-bonds and the dispersion interactions. Our approaches have successfully interpreted the observed spectra in the gas phase. The proposed structure database also reveals a possible dominant cluster size in the liquid phase, which is different from Linus Pauling’s and other literature’s suggestions.

Keywords: Atomic and molecular spectroscopy, Harmonic approximation, Methanol, Hydrogen bond