Three DFT exchange-correlation functionals (PW91, RPBE, and HCTH) are used in the anhydrous serine simulation. The experimental data are listed for comparison.
Two structures of the monohydrated serine. In structure A, the O atom of the H2O forms a H-bond with the H atom of the –NH3 + group. In structure B, the O atom of the H2O forms a H-bond with the H atom of the –OH group.
The simulated spectra of the two kinds of monohydrated serine. The spectra of the type A and B combinations are complementary with the peaks at 367, 423, and 448 cm−1.
When the –NH3 + and –OH groups of different serine molecules form H-bonds with the same O atom of the H2O, the calculated spectrum cannot match the experimental spectrum.
The superposition of the spectra of the type A and B combinations is summed with different ratios to indicate that both can coexist in the real system.
Bond lengths and angles for the anhydrous serine without H-bondings.
Assignment of anhydrous serine vibration modes with PW91 XC.
The details of the H-bonds involving H2O in the two monohydrated serine models.
Bond lengths and angles for the serine molecules without H-bondings in the two monohydrated models.
Assignment of monohydrated serine vibration modes with PW91 XC.
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