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Title: The structure of liquid water up to 360 MPa from x-ray diffraction measurements using a high Q-range and from molecular simulation

In this study, x-ray diffraction measurements of liquid water are reported at pressures up to 360 MPa corresponding to a density of 0.0373 molecules per Å 3. The measurements were conducted at a spatial resolution corresponding to Q max = 16 Å -1. The method of data analysis and measurement in this study follows the earlier benchmark results reported for water under ambient conditions having a density of 0.0333 molecules per Å 3 and Q max = 20 Å -1 [J. Chem. Phys. 138, 074506 (2013)] and at 70°C having a density of 0.0327 molecules per Å 3 and Q max = 20 Å -1 [J. Chem. Phys. 141, 214507 (2014)]. The structure of water is very different at these three different T and P state points and thus they provide the basis for evaluating the fidelity of molecular simulation. Measurements show that at 360 MPa, the 4 waters residing in the region between 2.3 and 3 Å are nearly unchanged: the peak position, shape, and coordination number are nearly identical to their values under ambient conditions. However, in the region above 3 Å, large structural changes occur with the collapse of the well-defined 2nd shell and shifting of highermore » shells to shorter distances. The measured structure is compared to simulated structure using intermolecular potentials described by both first-principles methods (revPBE-D3) and classical potentials (TIP4P/2005, MB-pol, and mW). The DFT-based, revPBE-D3, method and the many-body empirical potential model, MB-pol, provide the best overall representation of the ambient, high-temperature, and high-pressure data. Finally, the revPBE-D3, MB-pol, and the TIP4P/2005 models capture the densification mechanism, whereby the non-bonded 5th nearest neighbor molecule, which partially encroaches the 1st shell at ambient pressure, is pushed further into the local tetrahedral arrangement at higher pressures by the more distant molecules filling the void space in the network between the 1st and 2nd shells.« less
ORCiD logo [1] ;  [2] ;  [2] ;  [2] ;  [3] ;  [4] ;  [2] ;  [5]
  1. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS), X-Ray Science Division; Stony Brook Univ., NY (United States). Mineral Physics Institute
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Physical and Computational Sciences Division
  3. Stony Brook Univ., NY (United States). Mineral Physics Institute; Stony Brook Univ., NY (United States). Department of Geosciences; Brookhaven National Lab. (BNL), Upton, NY (United States). Photon Sciences Division
  4. Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin (France); Vietnam Academy of Science and Technology (Vietnam). Center for Quantum Electronics, Institute of Physics
  5. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS), X-Ray Science Division
Publication Date:
Report Number(s):
Journal ID: ISSN 0021-9606
Grant/Contract Number:
SC00112704; FG02-09ER46650; AC02-06CH11357; BES DE-FG02-09ER46650
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 144; Journal Issue: 13; Journal ID: ISSN 0021-9606
American Institute of Physics (AIP)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1245490