Calorimetric Signature of Deuterated Ice II: Turning an Endotherm to an Exotherm.

ABSTRACT: Calorimetric studies on ice II reveal a surprising H₂O/D₂O isotope effect. While the ice II to ice Ic transition is endothermic for H₂O, it is exothermic for D₂O samples. The transition enthalpies are +40 and -140 J/mol, respectively, where such a sign change upon isotope substitution is unprecedented in ice research. To understand the observations we employ force field calculations using two water models known to perform well for H₂O ice phases and their vibrational properties. These simulations reveal that the isotope effect can be traced back to zero-point energy. q-TIP4P/F fares better and is able to account for approximately three-fourths of the isotope effect, while MB-pol only catches approximately one-third. Phonon and configur

SUBMITTER: Fuentes-Landete V 

PROVIDER: S-EPMC7528406 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature