The hydrogen-bond collective dynamics in liquid methanol
The relatively simple molecular structure of hydrogen-bonded (HB) systems is often belied by their exceptionally complex thermodynamic and microscopic behaviour. For this reason, after a thorough experimental, computational and theoretical scrutiny, the dynamics of molecules in HB systems still eludes a comprehensive understanding. Aiming at shedding some insight into this topic, we jointly used neutron Brillouin scattering and molecular dynamics simulations to probe the dynamics of a prototypical hydrogen-bonded alcohol, liquid methanol.
Caption Fig.1: Fit of neutron Brillouin data obtained for liquid deuterated methanol at T = 298 K at Q= 0.4 and 10 nm-1. The red line is the result of a linear combination of the simulation (blue dots connected by a solid line) and multiple scattering (green dashes) data to the experimental spectra.
Caption Fig.2: Frequencies of longitudinal (open symbols) and transverse (closed symbols) modes for liquid deuterated methanol at T=298K. The black line is the linear dispersion corresponding to the adiabatic sound speed of cs = 1100 m/s while the dashed line corresponds to an apparent propagation velocity of ~2750 m/s.
Caption Fig.3: Schematic representation of longitudinal and transverse modes contributing to the THz spectrum of liquid water and methanol.
Reference: S. Bellissima, M. A. Gonzalez, U. Bafile, A. Cunsolo, F. Formisano, S. De Panfilis, and E. Guarini, “Switching of hydrogen-bond-driven excitation modes in liquid methanol”, Sci. Rep. 7, Article number: 10057 (2017).