Equilibrium chemistry down to 100 K
Equilibrium chemistry down to 100 K
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低至 100 K 的平衡化学
DOI：
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发表时间：
2017
影响因子：
6.5
通讯作者：
J. Stock
中科院分区：
文献类型：
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作者：
P. Woitke;Ch. Helling;G. Hunter;J. Millard;G. Turner;M. Worters;J. Blecic;J. Stock
我们已经介绍了一个快速和通用的计算机代码，GGCHEM，以确定气体的化学成分在热化学平衡低至100 K，有或没有平衡冷凝。我们回顾了来自几个来源的分子平衡常数kp(T)的数据，并讨论了哪些功能适合于低温。我们将我们的结果与另一种化学平衡程序进行了比较。我们从NIST-JANAF数据库和地球物理数据库SUPCRTBL中收集了大约200种固体和液体物质的吉布斯自由能ΔGf。我们讨论了太阳丰度元素在100 K以下相平衡时的缩聚顺序。一旦主要的镁硅酸盐Mg2SiO4[s]和MgSiO3[s]形成，尘埃与气体的质量比就会跳跃到0.0045左右，这比通常假设的0.01要低得多。发现硅酸盐缩聚使气体中的碳氧比（C/O）从太阳值~0.55提高到~0.71，并且，由于水和羟基进入固体基质的额外摄入量，层状硅酸盐的形成在~400 K以下的温度下使气体的C/O进一步提高到约0.83。金属钨(W)是发现的第一个在1600-2200 K（取决于压力）左右变得热力学稳定的冷凝物，在随后的材料如二氧化锆（ZrO2）或刚玉（Al2O3）可以凝结之前的几百开尔文。我们简要地讨论了钨是否可以为天体物理尘埃的形成提供第一个种子粒子，尽管它的丰度是硅丰度的~2 × 10−7倍。
We have introduced a fast and versatile computer code, GGCHEM, to determine the chemical composition of gases in thermo-chemical equilibrium down to 100 K, with or without equilibrium condensation. We have reviewed the data for molecular equilibrium constants, kp(T), from several sources and discussed which functional fits are most suitable for low temperatures. We benchmarked our results against another chemical equilibrium code. We collected Gibbs free energies, ΔGf⊖, for about 200 solid and liquid species from the NIST-JANAF database and the geophysical database SUPCRTBL. We discussed the condensation sequence of the elements with solar abundances in phase equilibrium down to 100 K. Once the major magnesium silicates Mg2SiO4[s] and MgSiO3[s] have formed, the dust to gas mass ratio jumps to a value of about 0.0045 which is significantly lower than the often assumed value of 0.01. Silicate condensation is found to increase the carbon to oxygen ratio (C/O) in the gas from its solar value of ~0.55 up to ~0.71, and, by the additional intake of water and hydroxyl into the solid matrix, the formation of phyllosilicates at temperatures below ~400 K increases the gaseous C/O further to about 0.83. Metallic tungsten (W) is the first condensate found to become thermodynamically stable around 1600–2200 K (depending on pressure), several hundreds of Kelvin before subsequent materials such as zirconium dioxide (ZrO2) or corundum (Al2O3) can condense. We briefly discuss whether tungsten, despite its low abundance of ~2 × 10−7 times the silicon abundance, could provide the first seed particles for astrophysical dust formation.
SUPCRTBL：SUPCRT92 的修订和扩展热力学数据集和软件包
影响因子：
4.4
作者：
Zimmer, Kurt;Zhang, Yilun;Lu, Peng;Chen, Yanyan;Zhang, Guanru;Dalkilic, Mehmet;Zhu, Chen
通讯作者：
Zhu, Chen