Absorption spectra of liquid water at 300 K are calculated from both classical and density functional theory molecular dynamics simulation data, which together span from 1 MHz to hundreds of THz, agreeing well with experimental data qualitatively and quantitatively over the entire range, including the IR modes, the microwave peak, and the intermediate THz bands. The spectra are decomposed into single-molecular and collective components, as well as into components due to molecular reorientations and changes in induced molecular dipole moments. These decompositions shed light on the motions underlying the librational and translational (hydrogen-bond stretching) bands at 20 and 5 THz, respectively; interactions between donor protons and acceptor lone pair electrons are shown to be important for the line shape in both librational and translational regimes, and in- and out-of-phase librational dimer modes are observed and explored.

中文翻译：

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探索模拟水从MHz到红外的吸收光谱。

根据经典和密度泛函理论分子动力学模拟数据计算了300 K时液态水的吸收光谱，这些数据的跨度从1 MHz到数百THz，在包括红外模式在内的整个范围内在质量和数量上均与实验数据吻合，微波峰值和中间THz频段。光谱被分解成单分子和集体成分，以及由于分子重新取向和诱导的分子偶极矩的变化而分解成的成分。这些分解揭示了分别以20和5 THz的自由和平移（氢键拉伸）带所依据的运动。