Dresden 2026 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 14: Liquid and Amorphous Materials I
MM 14.3: Talk
Tuesday, March 10, 2026, 12:00–12:15, SCH/A315
Volume increase of silica glass due to water intercalation and silanol group formation — Manuel Enns1, Wolfgang Körner1, Christian Elsässer1,2, and •Daniel F. Urban1,2 — 1Fraunhofer Institut für Werkstoffmechanik IWM, Freiburg, Germany — 2Freiburger Materialforschungszentrum FMF, Albert-Ludwigs-Universität Freiburg, Germany
We present a theoretical study on the change of volume of silica glass due to the intercalation of molecular water and the formation of silanol groups. By a statistical representative set of density functional theory calculations, we obtained a volume increase per mole of molecular water in amorphous SiO2 of 2.5 cm3/mol. In comparison, for the reaction of water to silanol groups we found on average a 3.5 times larger volume increase of 8.7 cm3/mol. Our results show that the exothermic dissolution of H2O into silanol pairs is not restricted to small rings of size three and four. We find an equal distribution of reaction energies over all ring sizes which we explain by the structural relaxation and the related energy gain of the entire amorphous neighbourhood. Statistically, most exothermic dissolution of H2O may happen at five-membered rings since they outnumber the three- and four-membered rings in amorphous SiO2. Our findings shed new light on the underlying mechanisms and the size of the volume change of the water intercalation in silica glass and we discuss our findings with respect to previous experimental and theoretical work.
Keywords: quartz glass; silanol group formation; density functional theory; amorphous network; structural defect