In this work, five Mg-silicate glasses with compositions between MgSiO\(_3\) and Mg\(_2\)SiO\(_4\) were synthesized by aerodynamic levitation combined with laser melting. Low-temperature heat capacity (\(C_p\)) was measured (by relaxation calorimetry in the range 2–310 K) for all of them, with the resulting vibrational entropies at T = 298.15 K: sample MG50 with composition Mg\(_{0.996}\)SiO\(_{2.996}\) and entropy 72.88 J mol\(^{-1}\) K\(^{-1}\); MG54 Mg\(_{1.174}\)SiO\(_{3.174}\) 78.54; MG58 Mg\(_{1.364}\)SiO\(_{3.364}\) 85.05; MG62 Mg\(_{1.611}\)SiO\(_{3.611}\) 91.40; and MG67 Mg\(_{1.907}\)SiO\(_{3.907}\) 102.75. Heat capacity of the glasses is higher than that of the corresponding crystal mixtures below 200 K but plunges below the C\(_{p,\mathrm{crystal}}\) at higher temperatures. High-temperature \(C_p\) was measured (by differential scanning calorimetry in the range 300–970 K) for MG50 and MG67 up to \(\approx \) 1000 K. Using our \(C_p\) data, selected data for entropies of fusion, \(C_p\) of crystals, and fictive temperatures, the configurational entropy (\(S_\mathrm{conf}\)) at glass transition temperature (\(T_\mathrm{g}\)) were calculated. For the near-forsterite glass MG67, the \(S_\mathrm{conf}\) is 1.9 J mol\(^{-1}\) K\(^{-1}\) at \(T_\mathrm{g}\) = 1040 K. As this small value is a difference of several large numbers, its uncertainty is relatively high; we consider a conservative estimate of 15 J mol\(^{-1}\) K\(^{-1}\). Using the expression \(\log \eta = A + B/[T S_\mathrm{conf}(T)]\), the available experimental viscosities (\(\eta \)) and the temperature-dependent configurational entropy from our work, we refined the parameters \(A = -2.34\) and \(B = 76,500\) for this equation, with \(S_\mathrm{conf} (T) = 1.90+(83.7 \ln (T/1040))\). The configurational entropy for the enstatitic MG50 glass is 16.8 J mol\(^{-1}\) K\(^{-1}\) at \(T_\mathrm{g}\) = 1063 K. The presented data can be combined with enthalpies of formation and thermophysical properties of Mg-silicate glasses for models that could elucidate geological and geophysical observations in the crust and mantle of the Earth.

在这项工作中，通过空气动力学悬浮结合激光熔化合成了五种成分介于MgSiO \(_3\)和Mg \(_2\) SiO \(_4\)之间的Mg-硅酸盐玻璃。低温热容 ( \(C_p\) ) 被测量（通过弛豫量热法在 2-310 K 范围内），在T = 298.15 K 时产生的振动熵：样品 MG50 与成分 Mg \(_ {0.996}\) SiO \(_{2.996}\)和熵 72.88 J mol \(^{-1}\) K \(^{-1}\) ; MG54 Mg \(_{1.174}\) SiO \(_{3.174}\) 78.54; MG58 Mg \(_{1.364}\) SiO\(_{3.364}\) 85.05; MG62 Mg \(_{1.611}\) SiO \(_{3.611}\) 91.40; 和 MG67 Mg \(_{1.907}\) SiO \(_{3.907}\) 102.75。玻璃的热容高于 200 K 以下的相应晶体混合物的热容，但在较高温度下低于 C \(_{p,\mathrm{crystal}}\)。MG50 和 MG67的高温\(C_p\)被测量（通过 300-970 K 范围内的差示扫描量热法）达到\(\approx \) 1000 K。使用我们的\(C_p\)数据，选择数据用于融合熵，晶体的\(C_p\)，以及假想的温度，构型熵 ( \(S_\mathrm{conf}\)) 在玻璃化转变温度 ( \(T_\mathrm{g}\) ) 下计算。对于近镁橄榄石玻璃 MG67，\(S_\mathrm{conf}\)为 1.9 J mol \(^{-1}\) K \(^{-1}\)在\(T_\mathrm{g }\) = 1040 K。由于这个小值是几个大数的差值，所以它的不确定性比较高；我们考虑 15 J mol \(^{-1}\) K \(^{-1}\)的保守估计。使用表达式\(\log \eta = A + B/[T S_\mathrm{conf}(T)]\)，可用的实验粘度（\(\eta \)）和来自我们的温度相关配置熵工作，我们改进了参数\(A = -2.34\)和\(B = 76,500\)对于这个方程，\(S_\mathrm{conf} (T) = 1.90+(83.7 \ln (T/1040))\)。在\(T_\mathrm{g}\) = 1063 K处，顽固性 MG50 玻璃的构型熵为 16.8 J mol \(^{-1}\) K \(^{-1}\)。所提供的数据可以结合镁-硅酸盐玻璃的形成焓和热物理性质，形成可以阐明地球地壳和地幔中地质和地球物理观测的模型。