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Title: Infrared signature of micro-hydration in the organophosphate sarin: An ab initio study

The infrared (IR) spectra of micro-hydrated Sarin•(H2O)n clusters containing between one and four explicit waters have been studied using ab initio density functional theory (DFT) methods. The phosphate group P=O bond vibration region (~1270 to 1290 cm–1) revealed the largest frequency variation with hydration, with a frequency red shift reflecting the direct hydrogen bond formation between the P=O of Sarin and water. Small variations to the P-F stretch (~810 to 815 cm–1) and the C-O-P vibrational modes (~995 to 1004 cm–1) showed that the water interactions with these functional groups were minor, and that the structures of Sarin were not extensively perturbed in the hydrated complexes. Increasing the number of explicit hydration waters produced only small vibrational changes in the lowest free energy complexes. These minor changes were consistent with a single water-phosphate hydrogen bond being the dominant structure, though a second water-phosphate hydrogen bond was observed in some complexes and was identified by an additional red shift of the P=O bond vibration. As a result, the H2O•H2O vibrational modes (~3450 to 3660 cm–1) increased in complexity with higher hydration levels and reflect the extended hydrogen bonding networks formed between the explicit waters in the hydrated Sarin clusters.
Authors:
 [1] ;  [1]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
OSTI Identifier:
1235332
Report Number(s):
SAND--2015-1636J
Journal ID: ISSN 1610-2940; 567435
Grant/Contract Number:
AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Journal of Molecular Modeling
Additional Journal Information:
Journal Volume: 21; Journal Issue: 7; Journal ID: ISSN 1610-2940
Publisher:
Springer-Verlag
Research Org:
Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
DTRA
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY ab initio; CWA; DFT; IR spectra; micro-hydration; sarin; solvent