Hydrogen Bond Thermodynamics in Aqueous Acid Solutions: A Combined DFT and Classical Force-Field Approach
Hydrogen Bond Thermodynamics in Aqueous Acid Solutions: A Combined DFT and Classical Force-Field Approach
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水溶液中的氢键热力学：结合 DFT 和经典力场方法
DOI：
10.1021/acs.jpca.2c04124
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Milner, Scott T.
中科院分区：
文献类型：
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作者：
Tran, Bolton;Cai, Yusheng;Janik, Michael J.;Milner, Scott T.
水溶液和酸性溶液中氢键的热力学对酸反应化学的动力学和热力学有重要影响。在这项工作中，我们利用多尺度方法，结合密度泛函理论（DFT）和经典分子动力学（MD）来模拟酸性溶液中的氢键热力学。利用热力学循环，我们将溶液相自由能分解为气相自由能和溶剂化自由能。通过计算两个水分子（H2O -···- H2O）之间的水相氢键自由能、h30 +阳离子转化为H5O2+阳离子的自由能和质子化水团簇（h30 + -···- H2O和H5O2+ -···- H2O）的氢键自由能，验证了该DFT/MD方法。计算的H2O -···- H2O的平衡氢键自由能非常准确，特别是考虑到对热力学循环的大个体贡献。转到阳离子，我们发现离子比h30 +稳定大约1-2kBT。这个小的自由能差允许两个理想基序之间的热波动，与光谱和模拟研究一致。最后，发现溶液中H+阳离子与H2O之间的氢键自由能比两个H2O之间的氢键自由能强，但由于溶液中的介电屏蔽而远低于真空中的氢键自由能。总之，我们的研究结果表明，DFT/MD方法有望应用于模拟凝聚相中的氢键和质子转移热力学。
The thermodynamics of hydrogen bonds in aqueous and acidic solutions significantly impacts the kinetics and thermodynamics of acid reaction chemistry. We utilize in this work a multiscale approach, combining density functional theory (DFT) with classical molecular dynamics (MD) to model hydrogen bond thermodynamics in an acidic solution. Using thermodynamic cycles, we split the solution phase free energy into its gas phase counterpart plus solvation free energies. We validate this DFT/MD approach by calculating the aqueous phase hydrogen bond free energy between two water molecules (H2O–···–H2O), the free energy to transform an H3O+cation into an H5O2+cation, and the hydrogen bond free energy of protonated water clusters (H3O+–···–H2O and H5O2+–···–H2O). The computed equilibrium hydrogen bond free energy of H2O–···–H2O is remarkably accurate, especially considering the large individual contributions to the thermodynamic cycle. Turning to cations, we find the ion to be more stable than H3O+by roughly 1–2kBT. This small free energy difference allows for thermal fluctuation between the two idealized motifs, consistent with spectroscopic and simulation studies. Lastly, hydrogen bonding free energies between either H+cation and H2O in solution were found to be stronger than between two H2O, though much less so than in vacuum because of dielectric screening in solution. Altogether, our results suggest the DFT/MD approach is promising for application in modeling hydrogen bonding and proton transfer thermodynamics in condensed phases.