First-principles investigation of equilibrium isotopic fractionation of O- and Si-isotopes between refractory solids and gases in the solar nebula
First-principles investigation of equilibrium isotopic fractionation of O- and Si-isotopes between refractory solids and gases in the solar nebula
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DOI：
10.1016/j.epsl.2011.12.029
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发表时间：
2012-02-15
影响因子：
5.3
通讯作者：
Lazzeri, Michele
中科院分区：
文献类型：
--
作者：
Javoy, Marc;Balan, Etienne;Lazzeri, Michele
基于密度泛函理论（DFT）的第一性原理方法可以计算小气体分子和晶体化合物的同位素配分函数，其精度相当。我们将这些方法应用于宇宙化学问题中感兴趣的几个物种，特别强调迄今为止在同位素宇宙化学中被忽视的分子：一氧化硅和一硫化硅。这些物种很可能在未来的宇宙化学研究中发挥重要作用，并已出现在与质量无关分馏（MIF）生成有关的研究中。我们探讨了这些分子与主要的气态太阳物种（CO，H2O）和一些关键的陨石矿物的平衡质量相关的分馏（ESTA）：结果的例子给出了二氧化硅富集的镁球粒和硅的硅固溶体的成因过程中的铁镍金属，一个可能的起始产品行星核心的SiO和SiS的同位素组成SiO的作用。结果表明，早期太阳一氧化硅的氧同位素组成可能位于交点处（δ O-18=2.12 ± 0.4%，δ O-17 = 1.1 ± 0.2%）。杨罗素线与对应于太阳系内主要天体的蓝线。这可能与自屏蔽模型框架下的太阳水丰度有关。在E-1000形成时，星云气体的δ Si-30（以SiS为主）约为-6%。(C)2011 Elsevier ay. All rights reserved.
First-principles methods based on density functional theory (DFT) allow the calculation of isotopic partition functions of small gaseous molecules and crystalline compounds with comparable levels of accuracy. We applied these methods to a few species of interest in cosmochemical problems, with a special emphasis on molecules up to now rather neglected in isotopic cosmochemistry: silicon monoxide and silicon monosulfide. These species are likely to play an important role in future cosmochemical studies and already appear in studies such as those related to mass independent fractionation (MIF) generation. We explore the equilibrium mass dependent fractionation (MDF) of these molecules with major gaseous solar species (CO, H2O) and some key meteorite minerals: examples of results are given for the role of SiO on silica enrichment of magnesian chondrules and for the isotopic composition of SiO and SiS during the genesis of silicon solid-solutions in chondritic Fe-Ni metal, a possible starting product for planetary cores. It is shown that the oxygen isotopic composition of early solar silicon monoxide likely lays at the intersection (delta O-18=2.12 0.4%, delta O-17 = 1.1 +/- 0.2%.) of the Young Russell line with the MDF lines corresponding to the main inner solar system bodies. This can be related to solar water abundance in the frame of self-shielding models. At the time of E chondrites' formation the delta Si-30 of the nebular gas, dominated by SiS, was similar to-6%. (C) 2011 Elsevier ay. All rights reserved.