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Seven solvents represented by nonpolarizable all-atom force fields and a series of idealized variable-charge solvents were used to span the range of solvent polarities (hydrogen bonding) studied experimentally. Simulated spectra capture the solvent dependence observed, as well as the relationship between the frequencies of water libration (\u03bdL) and OH stretching bands (\u03bdOH). In more strongly interacting solvents, simulated \u03bdL are \u223c20% higher than those of experiment. In all solvents, the simulated spectra are composites of rotational motions about the two axes perpendicular to water\u2019s dipole moment, and the different frequencies of these two motions are responsible for the breadth of the libration band and the bimodal shape observed in halide ionic liquids. Simulations overestimate the separation of these two components in most solvents. The character of water rotational motions changes markedly with solvent polarity, from quasi-free rotation in nonpolar and weakly polar solvents to highly constrained libration in strongly hydrogen bonding environments. The changeover to librational motions dominating the spectrum occurs between solvents such as benzene (\u03bdL \u223c 250\u00a0cm\u22121) and acetonitrile (\u03bdL \u223c 400\u00a0cm\u22121). For solvents in the latter category, the mean frequency of the experimental FIR band provides a direct measure of mean-squared torques and, therefore, force constants associated with interactions constraining water\u2019s librational motion.<\/jats:p>","DOI":"10.1063\/5.0156511","type":"journal-article","created":{"date-parts":[[2023,7,18]],"date-time":"2023-07-18T06:56:20Z","timestamp":1689663380000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":3,"title":["What do far-infrared spectra of solitary water in \u201cwater-in-solvent\u201d systems reveal about water\u2019s solvation and dynamics?"],"prefix":"10.1063","volume":"159","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3369-5868","authenticated-orcid":false,"given":"Sourav","family":"Palchowdhury","sequence":"first","affiliation":[{"name":"Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2467-5056","authenticated-orcid":false,"given":"Kallol","family":"Mukherjee","sequence":"additional","affiliation":[{"name":"Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1633-1472","authenticated-orcid":false,"given":"Mark","family":"Maroncelli","sequence":"additional","affiliation":[{"name":"Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"317","published-online":{"date-parts":[[2023,7,18]]},"reference":[{"key":"2023071810555838500_c1","doi-asserted-by":"publisher","first-page":"7190","DOI":"10.1021\/acs.chemrev.6b00504","article-title":"Application of ionic liquids to energy storage and conversion materials and devices","volume":"117","year":"2017","journal-title":"Chem. 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