title: Partial pair correlation functions of low-density supercritical water determined by neutron diffraction with the H/D isotopic substitution method.
abstract: Neutron diffraction measurements were carried out on H/ D isotopically substituted water in the low-density supercritical condition (T = 673 K, P = 26.3 MPa, and rho = 0.0068 molecules.A-3) in order to obtain direct information on the intermolecular partial structure functions, gHH inter(r), gOH inter(r), and gOO inter(r). In correspondence to the high-density supercritical water previously reported, the intermolecular nearest neighbor peaks in gHH inter(r), gOH inter(r), and gOO inter(r) are diffuse compared with the ambient ones. The nearest neighbor O...O distance (3.3 A) and its coordination number (2.6) were determined from the observed gOO inter(r). These results indicate that the orientational correlation between neighboring water molecules is considerably lost in low-density supercritical water. Small clusters involving a few water molecules are preferentially formed in low-density supercritical water, which is consistent with results obtained by previous IR and NMR studies.
authors: Institute of Material Structure Science, KEK, Tsukuba, Ibaraki 305-0801, Japan.
authors: Toshiya
authors: T
authors: Otomo
authors: Hiroki
authors: H
authors: Iwase
authors: Yasuo
authors: Y
authors: Kameda
authors: Nobuyuki
authors: N
authors: Matubayasi
authors: Keiji
authors: K
authors: Itoh
authors: Susumu
authors: S
authors: Ikeda
authors: Masaru
authors: M
authors: Nakahara