Die spezifischen Wärmen von CaO, Al₂O₃, CaOċAl₂O₃, 3CaOċAl₂O₃, 2CaOċSiO₂, 3CaOċSiO₂, 2CaOċAl₂O₃ċSiO₂ von 20° bis 1500° C

Abstract

Die spezifischen Wärmen von CaO, Al2O3, CaO·Al2O3, 3CaO·Al2O3, 2CaO·SiO2, 3CaO·SiO2, 2CaO·Al2O3·SiO2 bis 1500° werden mitgeteilt und die Abweichungen vom NEUMANN‐KOPP'schen Gesetz diskutiert. Das NEUMANN‐KOPP'sche Gesetz umfaßt die Erfahrung, daß in vielen Fällen die für die gekoppelten Schwingungen der Verbindungspartner benötigten Energiebeträge ebenso groß sind, wie die durch die Verbindungsbildung — Wachsen des inneren Drucks und damit Zunahme der molekularen Schwingungsfrequenzen — eingesparten Energien.

Thermodynamic modelling of the Ca–O system including 3rd generation description of CaO and CaO2

“…Consequently, a value of 40.35 J.mol -1 .K -1 is selected in this work for the absolute entropy of CaO, derived from the DFT phonon calculations in the quasi-harmonic approximation, which is slightly higher than the value of 38.21 J.mol -1 .K -1 compiled in the JANAF tables [41]. Above 300 K, the heat content as a function of temperature as derived from the phonon calculations by Pisch et al [24] were found to be in rather good agreement with most datasets [28,[30][31][32][33][35][36][37], except the heat content proposed by Roth et al [29] and Chekhovskoi et al [34]. Therefore, the latter datasets were not taken into account in the modelling.…”

“…The modelled heat content of crystalline CaO are plotted in Fig. 6 along with the available literature data [28][29][30][31][32][33][34]36] and results from previous modellings of the system [17,18]. A satisfactory fit of all the literature data was obtained, expect for the conflicting datasets from Chekhovskoi et al [34] and Roth et al [29].…”

“…The heat capacity data [25][26][27] in the literature are plotted in Fig. 1, and the available heat content data [28][29][30][31][32][33][34][35][36][37] represented in Fig. 2.…”

Ab initio-assisted assessment of the CaO-SiO2 system under pressure

“…Above ∼10 GPa the stable phase of CaSiO3 is orthorhombic (space group Pnma), and generally indicated as "Ca-Perovskite" (Ca-Pvsk). For Wo and PWo we adopted the heat capacity coefficients of Berman [42], which are based essentially on the calorimetric measurements of Krupka et al [110,111], White [112], Wagner [113], Elsner von Gronow and Schwiete [114] and disregard the low-to high-wollastonite phase transition detected by Richet et al [104]. We note however that below ∼1000 K the low-wollastonite data of Richet et al [104] are consistent with the heat capacity function selected in this work and a good consistency is observed also for PWo up to ∼2000 K (see Fig.…”