Temperature-Independent Nuclear Quantum Effects on the Structure of Water

Abstract

Nuclear quantum effects (NQEs) have a significant influence on the hydrogen bonds in water and aqueous solutions and have thus been the topic of extensive studies. However, the microscopic origin and the corresponding temperature dependence of NQEs have been elusive and still remain the subject of ongoing discussion. Previous x-ray scattering investigations indicate that NQEs on the structure of water exhibit significant temperature dependence [Phys. Rev. Lett. 94, 047801 (2005)PRLTAO0031-900710.1103/PhysRevLett.94.047801]. Here, by performing wide-angle x-ray scattering of H_{2}O and D_{2}O droplets at temperatures from 275 K down to 240 K, we determine the temperature dependence of NQEs on the structure of water down to the deeply supercooled regime. The data reveal that the magnitude of NQEs on the structure of water is temperature independent, as the structure factor of D_{2}O is similar to H_{2}O if the temperature is shifted by a constant 5 K, valid from ambient conditions to the deeply supercooled regime. Analysis of the accelerated growth of tetrahedral structures in supercooled H_{2}O and D_{2}O also shows similar behavior with a clear 5 K shift. The results indicate a constant compensation between NQEs delocalizing the proton in the librational motion away from the bond and in the OH stretch vibrational modes along the bond. This is consistent with the fact that only the vibrational ground state is populated at ambient and supercooled conditions.

Coherent X-rays reveal the influence of cage effects on ultrafast water dynamics

“…The current experiment probes the timescales between the ballistic regime and the cage effects. b The isothermal compressibility exhibits similar trends as the observed dynamics, when comparing experiments 60 with simulations 29 , 31 …”

“…The position of the first diffraction maximum shifts to lower Q upon cooling (Fig. 4b ) which correlates with the increase of tetrahedral coordination 27 , 31 , 43 . Figure 4c shows the cumulative average of β calculated on a single-shot basis for different temperatures (see Methods section).…”

“…Ultrashort X-ray pulses are used with variable pulse duration δt , ranging from 10 to 120 fs. Water droplets are injected into the experimental chamber and their temperature is varied over the range T = 253–328 K (see Methods section) 27 , 31 . A Cornell-SLAC Pixel Array Detector 32 (CSPAD) is used to record X-ray diffraction patterns over a broad momentum transfer range Q , allowing the distinction between frozen and supercooled liquid droplets on a shot-to-shot basis (see Methods section).…”

Nuclear quantum effects on the thermodynamic response functions of a polymorphic waterlike monatomic liquid

“…In the case of water and hydrogen, quantum effects are relevant in the proximity of the hypothesized LLCP [33,47]. Even in the supercritical region of the LLCP of water, H/D isotope substitution effects are observable [48,49]. In particular, as shown in Ref.…”

Observation of the thermal influenced quantum behaviour of water near a solid interface

“…The quantum mechanical treatments improved the classical results 5 – 7 , and quantum phenomena were obvious in confined water 8 – 10 . Recent issues are also to investigate the nuclear quantum effects 11 – 13 . However, the improvements have a certain distance from solving the mysteries of water for life.…”