共查询到19条相似文献，搜索用时 187 毫秒
1.
矿物在超临界溶液中的溶解度理论计算 总被引：10，自引：0，他引：10
本文概述了矿物在超临界溶液中的溶解度理论计算。讨论了平衡常数法和自由能法的热力学原理和计算机方法。两种方法都需要热力学数据,所不同的是平衡常数法需要的是反应平衡常数,而自由能法需要物种自由能数据。方法确定以后这些数据具备与否及其精度是这项研究的关键。此外当溶液中离子强度较大时,寻求一种适当的活度系数算法对溶解度理论计算也至关重要。 相似文献
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本文讨论了几个温度影响平衡的关系式，认为应用杂平衡常数的概念，可以把它们归结为温度对平衡常数的影响，从而使有关公式的推导更简捷明快。并从动力学和统计热力学的角度，推导出温度对平衡常数影响的关系式，指出上述影响的根源是温度影响粒子在能级中的玻兹曼分布 相似文献
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本文讨论了几个温度影响平衡的关系式，认为应用杂平衡常数的概念。可以把它们归结为温度对平衡常数的影响，从而使有关公式的推导更简捷明快，并从动力学和统计热力学的角度，推导出温度对平衡常数影响的关系式，指出上述影响的根源是温度影响粒子在能级中的玻兹曼分布。 相似文献
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总结不对称抽道集共反射面元叠加方法的工作经验，提出自由观测面自由反射界面不对称抽道集共反射面元叠加方法的处理思路和计算方法。在自由观测面的条件下，反射界面可分为简单倾斜平面、规则曲面和自由反射界面三种情况，针对不同情况讨论共反射面元的叠加方法。综合一般情况下的共反射面元叠加方法，提出了“鳞片法”的处理思路。 相似文献
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在控制氧逸度和酸度的条件下测定了３０℃时钯和铂氯络合物溶解度，将溶解度资料作用，求得它们的氯络合物种类分别为ＰｄＣｌ＾２－４和ＰｔＣｌ＾２－４，计算了相应反应式的平衡常数及推导了平衡常数与温度从属关系表达式，讨论了实验结果的地质意义。 相似文献
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利用激光诱导离解光谱自由定标法对一系列高纯度黄金样品进行定量分析与研究,初步证明了将此方法应用于黄金首饰成分测定的可行性。采用波长1 064nm的Nd∶YAG脉冲激光器激发黄金样品,波长范围为200～760nm的4CCD光纤光谱仪采集发射光谱,对Au元素质量分数范围为85.0%～99.6%的6件黄金标准样品进行激光诱导离解光谱测试。对所得黄金样品光谱中的Au,Cu,Ag三种元素分别选择合适的原子（离子）谱线代入自由定标法模型,通过所得参数拟合得到了所有元素原子（离子）的二维波尔兹曼平面曲线,并以此为基础进行元素的质量分数计算。激光诱导离解光谱自由定标法定量分析黄金样品中Au元素的质量分数与标准值的相对误差〈3%。 相似文献
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本文根据前人关于云母和黄玉的Ｆ－ＯＨ交换实验成果，分别建立了云母和黄玉的Ｆ－ＯＨ交换平衡常数方程，并系统阐述了推导这些方程的热力学原理以利用它们来估算云母＋黄玉平衡组合形成温度和共存流体组成的方法，最后讨论了这一方法的适用条件和存在问题。 相似文献
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Non-ideality in mineral solid solutions affects their elastic and thermodynamic properties, their thermobaric stability, and the equilibrium phase relations in multiphase assemblages. At a given composition and state of order, non-ideality in minerals is typically modelled via excesses in Gibbs free energy which are either constant or linear with respect to pressure and temperature. This approach has been extremely successful when modelling near-ideal solutions. However, when the lattice parameters of the solution endmembers differ significantly, extrapolations of thermodynamic properties to high pressures using these models may result in significant errors. In this paper, I investigate the effect of parameterising solution models in terms of the Helmholtz free energy, treating volume (or lattice parameters) rather than pressure as an independent variable. This approach has been previously applied to models of order–disorder, but the implications for the thermodynamics and elasticity of solid solutions have not been fully explored. Solid solution models based on the Helmholtz free energy are intuitive at a microscopic level, as they automatically include the energetic contribution from elastic deformation of the endmember lattices. A chemical contribution must also be included in such models, which arises from atomic exchange within the solution. Derivations are provided for the thermodynamic properties of n-endmember solutions. Examples of the use of the elastic model are presented for the alkali halides, pyroxene, garnet, and bridgmanite solid solutions. Elastic theory provides insights into the microscopic origins of non-ideality in a range of solutions, and can make accurate predictions of excess enthalpies, entropies, and volumes as a function of volume and temperature. In solutions where experimental data are sparse or contradictory, the Helmholtz free energy approach can be used to assess the magnitude of excess properties and their variation as a function of pressure and temperature. The formulation is expected to be useful for geochemical and geophysical studies of the Earth and other planetary bodies. 相似文献
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Mark S. Ghiorso Ian S. E. Carmichael Mark L. Rivers Richard O. Sack 《Contributions to Mineralogy and Petrology》1983,84(2-3):107-145
The compositions of liquids coexisting with experimentally grown crystals of olivine, plagioclase, clinopyroxene, orthopyroxene, leucite, spinel, rhombohedral oxide, melilite and potassium feldspar are used to define, through mass action expressions of liquid/solid equilibrium, compositional derivatives of the Gibbs free energy of mixing of naturally occuring silicate liquids as a function of temperature, pressure and the fugacity of oxygen. The available experimental data describe these derivatives over a range of compositions which includes basic magmas. Therefore, for silicate liquids in this composition range, the topology of the Gibbs free energy of mixing can be approximated from experimental determinations of its derivatives. The majority of the existing thermodynamic data on the liquid phase is consistent with the application of regular solution theory to model the free energy of mixing. Strictly symmetric, temperature and pressure independent, regular solution interaction parameters are calibrated from this phase equilibrium data using regression techniques which have their basis in inverse theory. These techniques generate numerically stable interaction parameters which incorporate inter-variable correlation and account for experimental uncertainty. The regular solution model fits the available data on anhydrous silicate liquids to within the accuracy of the thermodynamic database +/?550 cals). Extensions to regular solution theory allow water solubility in more silica rich liquids to be modelled somewhat less accurately (+/?750 cals). The topology of the excess free energy of mixing surface is strongly asymmetric, possessing a single multicomponent saddle point which defines a spinodal locus. Given this prediction of a multicomponent spinode, a mathematical procedure based upon minimisation of the Gibbs free energy of mixing is developed for the calculation of the compositions of coexisting immiscible liquids. Predicted binodal compositions substantially agree with elemental liquid/liquid partitioning trends observed in lavas. Calculations suggest that an immiscible dome, in temperature-composition space, intersects the liquidus field of the magma type tholeiite. Immiscible phenomena are predicted at sub-liquidus temperatures for the bulk compositions of more basic or alkalic lavas, but are absent in more siliceous rock types for temperatures of the metastable liquid down to 900 K. The regular solution model is used in four petrological applications. The first concerns a prediction of the binary olivine-liquid phase diagram. The calculated geometry exhibits a minimum near Fa75, which, though not in accord with experimental results on the pseudobinary system, compares quite favorably with olivine-liquid phase equilibria interpreted from rhyolites, namely that the olivine phenocrysts of rhyolites are more iron rich than their coexisting liquids. The second petrological example concerns estimating the depth of the source regions of several basic lavas whose compositions cover a range from ugandite to basaltic andesite. The third application is a calculation of the saturation temperatures and compositions of plagioclase and olivine in four experimental basaltic liquids and a prediction of the liquidus temperatures and first phenocryst compositions of the Thingmuli lava series of Eastern Iceland. Lastly, enthalpies of fusion are computed for a variety of stoichiometric compounds of geologic interest. These demonstrate good agreement with calorimetrically measured quantities 相似文献
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Determining the kinetics of many geologic and engineering processes involving solid/fluid interactions requires a fundamental understanding of the Gibbs free energy dependency of the system. Currently, significant discrepancies seem to exist between kinetic datasets measured to determine the relationship between dissolution rate and Gibbs free energy. To identify the causes of these discrepancies, we have combined vertical scanning interferometry, atomic force microscopy, and scanning electron microscopy techniques to identify dissolution mechanisms and quantify dissolution rates of albite single crystals over a range of Gibbs free energy (−61.1 < ΔG < −10.2 kJ/mol). During our experiments, both a previously dissolved albite surface exhibiting etch pits and a pristine surface lacking dissolution features were dissolved simultaneously within a hydrothermal, flow-through reactor. Experimental results document an up to 2 orders of magnitude difference in dissolution rate between the differently pretreated surfaces, which are dominated by different dissolution mechanisms. The rate difference, which persists over a range of solution saturation state, indicates that the dissolution mechanisms obey different Gibbs free energy dependencies. We propose that this difference in rates is the direct consequence of a kinetic change in dissolution mechanism with deviation from equilibrium conditions. The existence of this kinetic “switch” indicates that a single, continuous function describing the relationship between dissolution rate and Gibbs free energy may be insufficient. Finally, we discuss some of the potential consequences of our findings on albite’s weathering rates with a particular focus on the sample’s history. 相似文献
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S. K. Saxena 《Contributions to Mineralogy and Petrology》1982,78(3):345-351
Pyroxenes are considered as ideal solid solutions of some real components (e.g. diopside or orthoenstatite) and some fictive or hypothetical components (e.g. orthodiopside or orthohedenbergite). Using the reversed experimental data in the CaO-MgO-SiO2 system, the Gibbs free energy of formation of fictive orthodiopside and of fictive clinoenstatite have been determined in the temperature range of 1,000 to 1,600 °K. The data on free energies of components in the binary system can be used to extend the fictive component model to the ternary CaSiO3-MgSiO3-FeSiO3 system. Using published phase diagrams on the pyroxene quadrilateral, Gibbs free energy of formation of fictive orthohedenbergite has been calculated. Application of the ideally mixing fictive component model to computation of phase equilibria leads to the determination of compositions of coexisting Fe-Mg-Ca pyroxenes at different temperatures.Abbreviations and symbols
G
f
0
Gibbs free energy of formation from the elements at 1 bar and temperature
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G
Ex
excess free energy of mixing in a solution
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G
molar Gibbs free energy
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R
gas constant
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H
enthalpy
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S
entropy
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T
absolute temperature
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P
pressure
- KJ/M
kilojoules per mole
- j
joules
- Opx
orthopyroxene
- Cpx
clinopyroxene
- H
hedenbergite
- D
diopside
- E
enstatite
- F
ferrosilite
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X
mole fraction
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K
equilibrium constant 相似文献
15.
碳酸盐倒退溶解模式的化学热力学基础——与H_2S有关的溶解介质及其与CO_2的对比 总被引：1，自引：1，他引：0
以化学热力学中的吉布斯自由能增量为基础,计算了与H2S(g)/ H2S(aq) /HS-/ H+/S2-系统有关反应在不同温度下的平衡常数,同时根据方解石和白云石在酸性条件下的溶解过程,获得了这两种碳酸盐矿物溶解过程中地层中流体pH值与PCO2、地层压力和埋藏深度的关系。在此基础上,对比了从地表到深埋藏的温度和压力条件下,与CO2和H2S有关的酸性介质对流体\[H+\]贡献的差异性,以及对于碳酸盐溶解作用的差异性。计算结果表明:1）无论以CO2还是以H2S作为溶解介质,温度增加和（或）PCO2增加,都会造成方解石和白云石溶解所需要的\[H+\]增加,在深埋藏相对高温和高压条件下,高PCO2条件会使得碳酸盐矿物的溶解更加困难,如果\[H+\]受到缓冲,CO2的增加不仅不能造成碳酸盐矿物的溶解,反而会造成碳酸盐矿物的沉淀;2）无论在何种酸性介质中,碳酸盐矿物的倒退溶解模式在化学上都是成立的,低温的成岩环境,深部地层中高温流体的向上运移、构造抬升所造成的温度降低（-ΔT）都会提高H2S和（或）CO2流体（也包括其它酸性介质）对碳酸盐矿物溶解能力;3）在地表和近地表条件下（几百米深度范围内）,在同时存在CO2和H2S的环境中,CO2对应酸的电离提供的\[H+\]略多于H2S对应酸的电离,与CO2有关的酸性流体对碳酸盐矿物溶解相对重要,而在深埋藏条件下、尤其是深度大于4 000 m的深埋藏地层中,H2S对应酸的电离提供的\[H+\]显著大于CO2,其对碳酸盐矿物的溶解更为重要,在存在硫酸盐还原作用的深埋藏地层中,碳酸盐的深部溶解作用会更为发育,这可能是川东北地区深埋藏条件下次生孔隙发育的重要原因之一。 相似文献
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Thermodynamics of sodium feldspar II: Experimental results and numerical calculations 总被引：1，自引：0，他引：1
The free energy, entropy and enthalpy of sodium feldspar in thermal equilibrium and in metastable states are derived from investigations of the heat capacities of albite, analbite, ordered and disordered Or31. The lattice strains of all stable and metastable states are calculated from the two-order parameter theory published in the preceding paper. This approach also allows one to distinguish between the influence of Al, Si order and of the displacive lattice distortion on the thermodynamic behaviour of albite. The thermal cross-over between high albite and low albite is found to be a smooth function of temperature. 相似文献
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Thermochemical data on several phases forming in the systemCaO-MgO-Al2O3-SiO2 have been tested for consistency in reproducingexperimental phase equilibrium relationships. Calorimetric dataon enthalpy, entropy and heat capacity have been adjusted withinexperimental errors and new data on some phases have been estimatedusing phase equilibrium data. The consistency of the data inreproducing phase equilibrium relations in the multicomponent-multiphasesystems has been tested by computing phase diagrams using themethod of minimization of total Gibbs free energy. The recentcalorimetric data on most phases can be used without any significantchange except for phases that show cation disorder. Disordercorrections have been added to the heat capacity data on gehlenite,anorthite, spinel and Ca-Tschermak. 相似文献
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本文介绍一亚固相线实验的早阶段结果。亚固相线实验产物可以分为稳定与亚稳组合,不稳定组合只存在于实验的初始材料中。在整个实验过程中,与实验初始材料总成分和实验条件有关的一系列平衡反应可以逐个依次发生,亚稳组合是中间反应的产物。在实验中要设法区分亚稳组合和稳定组合,并把亚稳组合转化为稳定组合。亚稳组合间的转化及最终稳定组合的形成都遵循自由能降低的原则。 相似文献
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The P–T partition function in statistical thermodynamics can be used to derive semi-empirical formulations of the Gibbs free energy G for minerals and fluids. Parameterization of these equations includes simultaneous regression of experimental heat capacity and molar volume data, allowing fitting, appraisal and optimization of various data sources, as required in the construction of internally consistent petrological data bases. This approach can also be extended to minerals with -transitions and to fluids by considering the Gibbs free energy as a function of pressure P, temperature T and an ordering parameter X, so that accurate modelled representation and extrapolation of the thermodynamic properties of large numbers of petrologically significant minerals and coexisting fluids can be attained. The ordering parameter is chosen to denote the equilibrium mole fraction (thermodynamic probability) of ordered clusters (structural units) in a substance when G(T,P, X)=min. The procedure is tested on existing experimental data for the system MgO–SiO2–H2O. The proposed Gibbs free energy formulation permits thermodynamic properties of minerals, fluids and phase equilibria to be described and extrapolated over a wide range of pressure (0–800 kbar) and temperature (20–3000 K), thus allowing effective use in thermodynamic data bases of petrological interest. 相似文献