Author's posts
Sep 30 2022
Vibrational Dynamics of Non-Crystalline Solids
The boson peak (BP) is an excess of vibrational states over the Debye law appearing at terahertz frequencies. It is found in all glasses and marks the crossover between the long-wavelength behavior, where the solid can be considered as an isotropic continuum, and the region where the wavelength of the sound wave starts to experience …
Jul 06 2022
A lecture hall dedicated to our late friend and colleague Paolo Verrocchio
On June 29th, a lecture hall was dedicated to our late friend and colleague Paolo Verrocchio. The ceremony was held in the PovoZero building, home of the departments of Physics and Mathematics. In the presence of Paolo’s family, the dedication plaque was unveiled by the Rector, prof. Flavio Deflorian, and by prof. Giorgio Parisi, Nobel …
Jun 01 2022
Impact of the Environment on the PNIPAM Dynamical Transition Probed by Elastic Neutron Scattering
By means of elastic incoherent neutron scattering, we investigated how the addition of stabilizing cosolvents (glycerol and glucose) affects the dynamics of hydrated PNIPAM chains at the pico- and nanosecond time scale, where a low-temperature dynamical transition is observed. From the elastic intensities, the atomic mean square displacements of the PNIPAM samples were extracted using …
Mar 28 2022
X-ray induced dynamics in borate glasses with different network connectivity
Hard x rays induce atomic dynamics in oxide glasses at doses low enough that the average structure is unchanged. X-ray photon correlation spectroscopy is used here to study this effect in a series of alkali borate glasses characterized by different network connectivity. The product of the x-ray dose rate per atom and the decay time …
Mar 16 2022
The role of polymer structure on water confinement in poly(N-isopropylacrylamide) dispersions
Poly(N-isopropylacrylamide) (PNIPAM) is a synthetic polymer that is widely studied for its thermoresponsive character. However, recent works also reported evidence of a low temperature (protein-like) dynamical transition around 225 K in concentrated PNIPAM suspensions, independently of the polymer architecture, i.e., both for linear chains and for microgels. In this work, we investigate water-polymer interactions by …
Jan 05 2022
New insights about the role of Na–K ratio on the vibrational dynamics of synthetic-basalt glasses
Basalts are among the most abundant igneous rocks on Earth. Originated from the rapid cooling of magma erupted by volcanoes, they are increasingly used as raw materials in glass and ceramic technology due to their unique physico-chemical properties. The characteristics of basalts, like the glass transition temperature, are strongly controlled by their structure, which is …
Jun 22 2021
Estimating the viscosity of volcanic melts from the vibrational properties of their parental glasses
The numerical modelling of magma transport and volcanic eruptions requires accurate knowledge of the viscosity of magmatic liquids as a function of temperature and melt composition. However, there is growing evidence that volcanic melts can be prone to nanoscale modification and crystallization before and during viscosity measurements. This challenges the possibility of being able to …
Feb 26 2021
Proteinlike dynamical transition of hydrated polymer chains
Combining elastic incoherent neutron scattering experiments at different resolutions with molecular dynamics simulations, we report the observation of a proteinlike dynamical transition in linear chains of poly(N-isopropylacrylamide). We identify the onset of the transition at a temperature Td of about 225 K. Due to a global fit procedure, we find quantitative agreement between measured and …
Feb 11 2021
Thermal annealing and phase transformation of serpentine-like garnierite
This study is focused on the vibrational and microstructural aspects of the thermally induced transformation of serpentine-like garnierite into quartz, forsterite, and enstatite occurring at about 620 °C. Powder specimens of garnierite were annealed in static air between room temperature and 1000 °C. The kinetic of the transformation was investigated by means of thermogravimetric and …
Dec 14 2020
Two-Component Dynamics and the Liquidlike to Gaslike Crossover in Supercritical Water
Molecular-scale dynamics in sub-to supercritical water is studied with inelastic X-ray scattering and molecular dynamics simulations. The obtained longitudinal current correlation spectra can be decomposed into two main components: A low-frequency (LF), gaslike component and a high-frequency (HF) component arising from the O-O stretching mode between hydrogen-bonded molecules, reminiscent of the longitudinal acoustic mode in …
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