Temperature-dependent dynamic structure factors S(Q, ω) for liquid water have been calculated using a composite model, which is based on the decoupling approximation of the mean square displacement of the water molecules into diffusion and solid-like vibrational parts. The solid-like vibrational part S vib (Q, ω) is calculated with the phonon expansion method established in the framework of the incoherent Gaussian approximation. The diffusion part S diff (Q, ω) relies on the Egelstaff-Schofield translational diffusion model corrected for jump diffusions and rotational diffusions with the Singwi-Sjölander random model and Sears expansion, respectively. Systematics of the model parameters as a function of temperature were deduced from quasi-elastic neutron scattering data analysis reported in the literature and from molecular dynamics (MD) simulations relying on the TIP4P/2005f model. The resulting S(Q, ω) values are confronted by means of Monte Carlo simulations to inelastic neutron scattering data measured with IN4, IN5, and IN6 time-of-flight spectrometers of the Institut Laue-Langevin (ILL) (Grenoble, France). A modest range of temperatures (283-494 K) has been investigated with neutron wavelengths corresponding to incident neutron energies ranging from 0.57 to 67.6 meV. The neutron-weighted multiphonon spectra deduced from the ILL data indicate a slight overestimation by the MD simulations of the frequency shift and broadening of the librational band. The descriptive power of the composite model was suited for improving the comparison to experiments via Bayesian updating of prior model parameters inferred from MD simulations. The reported posterior temperature-dependent densities of state of hydrogen in H 2 O would represent valuable insights for studying the collective coupling interactions in the water molecule between the inter-and intramolecular degrees of freedom.

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The CINEL code dedicated to generate the thermal neutron scattering files in ENDF-6 format for solid crystalline, free gas materials and liquid water is presented. Compared to the LEAPR module of the NJOY code, CINEL is able to calculate the coherent and incoherent elastic scattering cross sections for any solid crystalline materials. Specific material properties such as anharmonicity and texture can be taken into account in CINEL. The calculation of the thermal scattering laws can be accelerated by using graphics processing unit (GPU), which enables to remove the short collision time approximation for large values of momentum transfer. CINEL is able to generate automatically the grids of dimensionless momentum and energy transfers. The Sampling the Velocity of the Target nucleus (SVT) algorithm capable of determining the scattered neutron distributions is implemented in CINEL. The obtained distributions for free target nuclei such as hydrogen and oxygen are in good agreement with analytical results and Monte-Carlo simulations when incident neutron energies are above a few eV. The introduction of the effective temperature and the rejection step to the SVT algorithm shows improvements to the neutron up-scattering treatment of hydrogen bound in liquid water.

Experimental phonon densities of states of UO2 have been deduced from double-differential neutron scattering data measured at 300 K, 600 K and 900 K using the IN6 time-of-flight spectrometer of the Institute Laue-langevin (ILL). The comparison with ab intio phonon spectra obtained at the North Caroline South University from first-principle calculations confirms that harmonic vibrations of the atoms cannot accurately reproduce the phonon broadening related to the oxygen atoms.

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