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1. The Local Vibrational Mode Theory and Its Place in the Vibrational Spectroscopy Arena

   https://doi.org/10.1021/acs.jpca.2c05962  

   Kraka, Elfi; Quintano, Mateus; La Force, Hunter W.; Antonio, Juliana J.; Freindorf, Marek (December 2022, The Journal of Physical Chemistry A)
2. Weak and strong π interactions between two monomers—assessed with local vibrational mode theory

   https://doi.org/10.1139/cjc-2022-0254  

   Zou, Wenli; Freindorf, Marek; Oliveira, Vytor; Tao, Yunwen; Kraka, Elfi (January 2023, Canadian Journal of Chemistry)

   We introduce in this work a unique parameter for the quantitative assessment of the intrinsic strength of the π interaction between two monomers forming a complex. The new parameter is a local intermonomer stretching force constant, based on the local mode theory, originally developed by Konkoli and Cremer, and derived from the set of nine possible intermonomer normal vibrational modes. The new local force constant was applied to a diverse set of more than 70 molecular complexes, which was divided into four groups. Group 1 includes atoms, ions, and small molecules interacting with benzene and substituted benzenes. Group 2 includes transition metal hydrides and oxides interacting with benzene while Group 3 involves ferrocenes, chromocenes, and titanium sandwich compounds. Group 4 presents an extension to oxygen π–hole interactions in comparison with in-plane hydrogen bonding. We found that the strength of the π interactions in these diverse molecular complexes can vary from weak interactions with predominantly electrostatic character, found, e.g., for argon–benzene complexes, to strong interactions with a substantial covalent nature, found, e.g., for ferrocenes; all being seamlessly described and compared with the new intermonomer local mode force constant, which also outperforms other descriptors such as an averaged force constant or a force constant guided by the electron density bond paths. We hope that our findings will inspire the community to apply the new parameter also to other intermonomer π interactions, enriching in this way the broad field of organometallic chemistry with a new efficient assessment tool. 

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3. Metal–ring interactions in group 2 ansa -metallocenes: assessed with the local vibrational mode theory

   https://doi.org/10.1039/D4CP00225C  

   Antonio, Juliana J; Kraka, Elfi (May 2024, Physical Chemistry Chemical Physics)

   An exploration of group twoansa-metallocenes for solvent effects, interannular bridges, and quantitative bond strength through local mode analysis. 

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4. Capturing Individual Hydrogen Bond Strengths in Ices via Periodic Local Vibrational Mode Theory: Beyond the Lattice Energy Picture

   https://doi.org/10.1021/acs.jctc.1c00357  

   Nanayakkara, Sadisha; Tao, Yunwen; Kraka, Elfi (January 2022, Journal of Chemical Theory and Computation)
5. Coupled local mode method for simulating vibrational spectroscopy

   https://doi.org/10.1063/5.0119631  

   Hanson, Matthew D.; Corcelli, Steven A. (October 2022, The Journal of Chemical Physics)

   Experimental and theoretical studies have highlighted protonated water clusters (PWCs) as important models of the excess proton in aqueous systems. A significant focus has been characterizing the spectral signatures associated with different excess proton solvation motifs. Accurate vibrational frequency calculations are crucial for connecting the measured spectra to the structure of PWCs. In this paper, we extend and characterize a coupled local mode (CLM) approach for calculating the infrared spectra of PWCs using the [Formula: see text] cluster as a benchmark system. The CLM method is relatively low cost and incorporates the anharmonicity and coupling of OH vibrations. Here, we demonstrate the accuracy of the technique compared to experiments. We also illustrate the dependence of calculated spectral features on the underlying electronic structure theory and basis sets used in the local mode frequency and coupling calculations. 

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