Structure and Dynamics of Low-Density and High-Density Liquid Water at High Pressure.
Liquid water has a primary role in ruling life on Earth in a wide temperature and pressure range as well as a plethora of chemical, physical, geological, and environmental processes. Nevertheless, a full understanding of its dynamical and structural properties is still lacking. Water molecules are associated through hydrogen bonds, with the resulting extended network characterized by a local tetrahedral arrangement. Two different local structures of the liquid, called low-density (LDW) and high-density (HDW) water, have been identified to potentially affect many different chemical, biological, and physical processes. By combining diamond anvil cell technology, ultrafast pump-probe infrared spectroscopy, and classical molecular dynamics simulations, we show that the liquid structure and orientational dynamics are intimately connected, identifying the P-T range of the LDW and HDW regimes. The latter are defined in terms of the speeding up of the orientational dynamics, caused by the increasing probability of breaking and reforming the hydrogen bonds.
†LENS, European Laboratory for Non-linear Spectroscopy, Via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy.
Samuele
S
Fanetti
†LENS, European Laboratory for Non-linear Spectroscopy, Via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy.|‡Dipartimento di Chimica "Ugo Schiff" dell'Università degli Studi di Firenze, Via della Lastruccia 3, I-50019 Sesto Fiorentino, Firenze, Italy.
Andrea
A
Lapini
‡Dipartimento di Chimica "Ugo Schiff" dell'Università degli Studi di Firenze, Via della Lastruccia 3, I-50019 Sesto Fiorentino, Firenze, Italy.
Marco
M
Pagliai
†LENS, European Laboratory for Non-linear Spectroscopy, Via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy.|‡Dipartimento di Chimica "Ugo Schiff" dell'Università degli Studi di Firenze, Via della Lastruccia 3, I-50019 Sesto Fiorentino, Firenze, Italy.
Margherita
M
Citroni
†LENS, European Laboratory for Non-linear Spectroscopy, Via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy.|‡Dipartimento di Chimica "Ugo Schiff" dell'Università degli Studi di Firenze, Via della Lastruccia 3, I-50019 Sesto Fiorentino, Firenze, Italy.
Mariangela
M
Di Donato
§The Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera 11, I-34151 Trieste, Italy.
Sandro
S
Scandolo
†LENS, European Laboratory for Non-linear Spectroscopy, Via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy.|‡Dipartimento di Chimica "Ugo Schiff" dell'Università degli Studi di Firenze, Via della Lastruccia 3, I-50019 Sesto Fiorentino, Firenze, Italy.
Roberto
R
Righini
†LENS, European Laboratory for Non-linear Spectroscopy, Via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy.|‡Dipartimento di Chimica "Ugo Schiff" dell'Università degli Studi di Firenze, Via della Lastruccia 3, I-50019 Sesto Fiorentino, Firenze, Italy.
Roberto
R
Bini
diamond anvil cell; molecular dynamics; molecular liquids; rotational anisotropy; ultrafast spectroscopy