dorsal/arxiv
View SchemaHydration of Krypton and Consideration of Clathrate Models of Hydrophobic Effects from the Perspective of Quasi-Chemical Theory
| Authors | Henry S. Ashbaugh, D. Asthagiri, Lawrence R. Pratt, Susan B. Rempe |
|---|---|
| Categories | |
| ArXiv ID | physics/0211016 |
| URL | https://arxiv.org/abs/physics/0211016 |
Abstract
AIMD results on a liquid krypton-water system are compared to recent XAFS results for the radial hydration structure for a Kr atom in liquid water solution. The comparisons with the liquid solution results are satisfactory and significantly different from the radial distributions extracted from the data on the solid clathrate hydrate phase. The calculations also produce the coordination number distribution that can be examined for metastable coordination structures suggesting possibilities for clathrate-like organization; none are seen in these results. Clathrate pictures of hydrophobic hydration are discussed, as is the quasi-chemical theory that should provide a basis for clathrate pictures. Outer shell contributions are discussed and accurately estimated; they are positive and larger than the positive experimental hydration free energy of Kr(aq), implying that inner shell contributions must be negative. Clathrate-like inner shell coordination structures extracted from the simulation of the liquid, and then subjected to quantum chemical optimization, always decomposed. Interactions with the outer shell material are decisive in stabilizing coordination structures observed in liquid solution and in clathrate phases. The ``what are we to tell students'' question about hydrophobic hydration, often answered with structural models such as clathrate pictures, is then considered; we propose an alternative answer that is consistent with successful molecular theories of hydrophobic effects and based upon distinctive observable properties of liquid water. Considerations of parsimony, for instance Ockham's razor, then suggest that additional structural hypotheses in response to ``what are we to tell students'' aren't required at this stage
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"date_created": "2026-03-02T18:00:42.469000Z",
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"abstract": "AIMD results on a liquid krypton-water system are compared to recent XAFS\nresults for the radial hydration structure for a Kr atom in liquid water\nsolution. The comparisons with the liquid solution results are satisfactory and\nsignificantly different from the radial distributions extracted from the data\non the solid clathrate hydrate phase. The calculations also produce the\ncoordination number distribution that can be examined for metastable\ncoordination structures suggesting possibilities for clathrate-like\norganization; none are seen in these results. Clathrate pictures of hydrophobic\nhydration are discussed, as is the quasi-chemical theory that should provide a\nbasis for clathrate pictures. Outer shell contributions are discussed and\naccurately estimated; they are positive and larger than the positive\nexperimental hydration free energy of Kr(aq), implying that inner shell\ncontributions must be negative. Clathrate-like inner shell coordination\nstructures extracted from the simulation of the liquid, and then subjected to\nquantum chemical optimization, always decomposed. Interactions with the outer\nshell material are decisive in stabilizing coordination structures observed in\nliquid solution and in clathrate phases. The ``what are we to tell students\u0027\u0027\nquestion about hydrophobic hydration, often answered with structural models\nsuch as clathrate pictures, is then considered; we propose an alternative\nanswer that is consistent with successful molecular theories of hydrophobic\neffects and based upon distinctive observable properties of liquid water.\nConsiderations of parsimony, for instance Ockham\u0027s razor, then suggest that\nadditional structural hypotheses in response to ``what are we to tell\nstudents\u0027\u0027 aren\u0027t required at this stage",
"arxiv_id": "physics/0211016",
"authors": [
"Henry S. Ashbaugh",
"D. Asthagiri",
"Lawrence R. Pratt",
"Susan B. Rempe"
],
"categories": [
"physics.bio-ph",
"physics.chem-ph"
],
"title": "Hydration of Krypton and Consideration of Clathrate Models of Hydrophobic Effects from the Perspective of Quasi-Chemical Theory",
"url": "https://arxiv.org/abs/physics/0211016"
},
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