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首页> 外文期刊>The American mineralogist >Defect contributions to the heat capacities and stabilities of some chain, ring, and sheet silicates, with implications for mantle minerals
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Defect contributions to the heat capacities and stabilities of some chain, ring, and sheet silicates, with implications for mantle minerals

机译：缺陷对某种链条，环和硅酸盐的热量和稳定性的缺陷贡献，具有披风矿物的影响

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摘要

At temperatures less than similar to 1500 K, previously published C-P data demonstrate that the heat capacities of orthoenstatite, proto-enstatite, diopside, and pseudowollastonite include primarily Debye type vibrational and anharmonic contributions, whereas the alkali chain, sheet, and ring silicates, Na2SiO3, Li2SiO3, K2SiO3, and Na2Si2O5 include a third contribution. The third contribution to C-P arises from defect formation due to the mobility Na, K, Li, and O2-. The contribution becomes apparent at temperatures above 700-800 K for Na and K silicates, and above 900-1000 K for Li metasilicate. With strong thermal agitation, alkali-non-bridging oxygen (NBO) bonds are ruptured with the cations exiting their structural sites to occupy interstitial sites, thereby producing intrinsic Frenkel defects, which contribute to the C-P of the alkali silicates. The magnitudes of the C-P defect contributions correlate inversely with cation-oxygen bond strengths, as measured by bond dissociation energies. K-O and Na-O bond strengths are weak (239 and 257 kJ/mol) and defect contributions are large for these alkali chain, ring, and sheet silicates. The greater bond strength of Li-O (341 kJ/mol) correlates with a weaker defect contribution to the C-P of Li2SiO3. Mg-O and Ca-O bonds are stronger still (394 and 464 kJ/mol) and no C-P defect contributions are observed for the pyroxenes and pseudowollastonite up to similar to 1500 K.
机译：在低于1500K的温度下，之前公布的C-P数据表明，正顽辉石、原顽辉石、透辉石和假硅灰石的热容主要包括德拜型振动和非谐贡献，而碱链、片状和环状硅酸盐、Na2SiO3、Li2SiO3、K2SiO3和Na2Si2O5包括第三种贡献。对C-P的第三个贡献来自于迁移率Na、K、Li和O2-导致的缺陷形成。当钠和钾硅酸盐温度高于700-800 K，锂偏硅酸盐温度高于900-1000 K时，这种贡献变得明显。在强烈的热搅拌下，碱-非桥氧（NBO）键断裂，阳离子离开其结构位置，占据间隙位置，从而产生固有的Frenkel缺陷，这有助于碱硅酸盐的C-P。C-P缺陷贡献的大小与通过键离解能测量的阳离子-氧键强度成反比。K-O和Na-O键强度较弱（239和257 kJ/mol），这些碱链、环和片状硅酸盐的缺陷贡献较大。Li-O的键强度（341 kJ/mol）越大，缺陷对Li2SiO3的C-P贡献越小。Mg-O和Ca-O键仍然更强（394和464 kJ/mol），对于高达1500K的辉石和假硅灰石，未观察到C-P缺陷贡献。

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