Ti-O体系化合物的生成吉布斯自由能的计算与分析

应用氧势递增原理对Ti-O体系中24种化合物的标准生成吉布斯自由能DfG0进行了计算分析. 结果显示,1304 K时Ti26O51与Ti28O55平衡的氧势和Ti24O47与Ti26O51平衡的氧势违背了氧势递增原理,表明Ti24O47, Ti26O51和Ti28O55三种物质的DfG0数据中至少一个有误. 在详细介绍用氧势递增原理和拟抛物线规则估算DfG0方法的基础上,分别对这3种氧化物的DfG0进行了估算,两种方法的计算结果一致,1304 K时DfG0Ti24O47=-16785.366±0.011 kJ/mol, DfG0Ti26O51= -18202.261±0.021 kJ/mol, DfG0Ti284O55=-19619.080±0.008 kJ/mol. 对估算结果分析认为,原Ti26O51的DfG0有误的可能性最大. 依据评估后的数据,以碳热还原和氢气还原TiO2制备了Ti4O7.     

Simple Method for Prediction of the Standard Gibbs Free Energy of Formation of Energetic Compounds

A reliable simple method for prediction of the standard Gibbs energy of formation (Δ_fG^θ) of energetic compounds containing nitroaromatic, acyclic, and cyclic nitramine, nitrate ester, and nitroaliphatic compounds is introduced herein. The method is based on the contribution of elemental composition (Δ_fG_elem^θ) and the correcting function for the presence of additive and non‐additive molecular fragments (Δ_fG_corr^θ). In presence of some molecular moieties, Δ_fG_corr^θ may increase or decrease the value of Δ_fG_elem^θ, depending on the intermolecular interactions. The experimental root‐mean‐square error (RMSE) of the novel correlation (22.7 kJ mol⁻¹) is quite good. For some energetic compounds, where the computed values of two complex models of the quantitative structure‐property relationship (QSPR) theory were available, the experimental RMSE developed by the new method is smaller than the values obtained by QSPR method.     

定标粒子理论研究胶束形成过程的热力学特征

本文综合考虑表面活性剂在形成胶束过程的热力学特征，在Ｎａｎｄｉ等所得结果的基础上，采用定标粒子理论计算了不同类型表面活性剂形成胶束过程中Ｇｉｂｂｓ自由能的变化。结果表明，这种改进的方法计算精度更高，而且间接地说明两性分子热力学特征在一定范围内能够很好地满足同系线性规律。     

Estimation of Gibbs Free Energy Functions

A computational method has been derived for the estimation of the molar heat capacity contribution to the Gibbs free energy function (fef_T^O) above 298°K. This method, which is based on the observed temperature invariance of certain ratios of the integrals of these molar heat capacity contributions, has been applied to the analysis of fef_T^Odata for metal carbides, nitrides, fluorides, borides, and silicides in the crystalline state. The estimated fef_T^Ofor a given compound is more accurate than that obtained by other known estimation techniques and permits a more accurate calculation of ΔG _T^O than is possible from the commonly used approximation ΔG _T^O=ΔG ₂₉₈^O- ΔG ₂₉₈^O.     

Gibbs Energy of Formation of Lead Zirconate

The Gibbs energy of formation of zirconia-saturated lead zirconate was determined by emf measurements on the solid state cells
and
at 800 to 1400 K. The results obtained differ significantly from those reported in the literature based on vapor-pressure measurements, using Knudsen effusion and transportation techniques and assuming that the vapor phase consisted entirely of monomeric PbO molecules. A reanalysis of the data obtained in the earlier vapor-pressure studies, using mass-spectrometric measurements on polymeric PbO species in the gas phase, gives Gibbs energies of formation of lead zirconate which are in better agreement with those obtained in this study. Recent electrochemical measurements using CaO-ZrO₂ and PbF₂ solid electrolytes are in good agreement with the present study. The results obtained in this study are also consistent with the phase diagram which shows decomposition of the zirconate to tetragonal zirconia and a liquid phase rich in PbO at 1843 K.     

液体混合的通用Gibbs自由能模型

鉴于活度系数与内压密切相关 ,修正了熟知的vanLaar理论 ,用Frank关系式替代了原理论推导中的vanderWaals流体内压 ,从而导得一个十分类似于Wohl方程的过量函数式 ,vanLaar方程、溶解度参数方程、Margules方程和Scatchard -Hamer方程等都是它的特例 .通过对过量熵贡献的修正 ,建立了一个活度系数方程 .它已被证明具有通用性 ,即不仅适用于各种小分子液体混合物 ,而且亦适用于各种高分子溶液 ,有比局部组成型方程更广的适用范围 .此外 ,由该Gibbs自由能模型还得到了溶解度参数一个新的定义 ,它比Hildebrand定义的溶解度参数更加广义 .     

Sensitivity of Phage Lambda upon Variations of the Gibbs Free Energy

We investigate the sensitivity of production rates (activities) of the regulatory proteins CI (repressor) and Cro at the right operator (O_R) of bacteriophage lambda. The DNA binding energies of CI, Cro, and RNA polymerase are perturbed to check the uncertainty of the activity, due to the experimental error, by means of a computational scattering method according to which the binding energies are simultaneously chosen at random around the literature values, with a width corresponding to the experimental error. In a grand canonical ensemble, with the randomly drawn protein-DNA binding energies as input, we calculate the corresponding activities of the promoters P_RM and P_R. By repeating this procedure we obtain a mean value of the activity that roughly corresponds to wild-type (unperturbed) activity. The standard deviation emerging from this scheme, a measure of the sensitivity due to experimental error, is significant (typically >20% relative to wild-type activity), but still the promoter activities are sufficiently separated to make the switch feasible. We also suggest a new, compact way of presenting repressor and Cro data.     

物理化学中吉布斯自由能理解及计算

物理化学概念及公式多、理论逻辑性强,学生感到理解困难、难以抓住主要内容。如何让学生抓住主线、理解和掌握重点、难点是每一位物理化学教师应该思考和探讨的问题。结合多年物理化学教学经验及学生反馈信息,体会到掌握吉布斯自由能（G）的相关知识对学好物理化学课程起决定作用。文章详细讨论总结了的G的提出背景、引出方式、计算方法等,并给出了详细计算公式及典型例题,对教师教及学生学具有很好参考价值。     

The Gibbs Free Energy Gradient Method for RDF gasification modelling

Starting from an equilibrium model for gasification, this research group has devised a new mathematical model, the so called Gibbs Free Energy Gradient Method Model (GMM). This model permits to bypass the semi-qualitative view, typical of equilibrium models, which assume very restrictive hypotheses such as equilibrium state for all the reactions involved in gasification process, complete conversion of carbon matter, gasification products in gas phase only. GMM model overcomes these limitations providing a quantitative point of view, even though the hypothesis of no tar production affects both models.GMM model has been applied to RDF gasification, supplying reliable results in the gasification process analysis. Model computations in terms of gas yield, gas composition, low heating value and H₂ yield, have been compared with literature results, showing that computed data are in good agreement with experimental ones.     

Gibbs Free Energy of Formation of Zircon from Measurement of Solubility in H2O

We exploited the large difference in the solubility of SiO₂ and ZrO₂ in H₂O to constrain precisely the Gibbs energy of formation of zircon (ZrSiO₄). Solubility in H₂O was determined at 800°C, 1.2 GPa, by weight loss of synthetic zircon crystals. The experiments yielded fine-grained monoclinic ZrO₂ as an incongruent solution product uniformly coating zircon crystals. Experiments on the ZrO₂-coated zircon crystals were also carried out with an initially slightly SiO₂-oversaturated fluid, causing weight gain by zircon regrowth. The mean SiO₂ concentration for forward and reverse experiments was 0.069±0.010 mol/kg H₂O (2σ). When combined with precise activity–composition measurements for aqueous SiO₂, the data constrain the Gibbs free energy of zircon from its oxides at 298 K, 10⁵ Pa, to be −19.30±1.16 kJ/mol (2σ). This determination is comparable in precision to the best measurements obtainable by more conventional methods, which suggests that determination of the thermochemical properties of other important ceramic materials may also be amenable to this method.     

表面张力和表面吉布斯自由能的严格证明

表面张力和表面吉布斯自由能是界面现象中非常重要的两个概念,表面张力定义为垂直作用在单位长度界面上的力,而表面吉布斯自由能是定温定压条件下,增加单位表面积引起系统吉布斯自由能的增量,实际上它们是从不同角度观察表面现象的同一物理量,但各教材中基本上没有详细的论述。文章从吉布斯自由能的实际意义角度对两者同一性进行严格的证明。     

色谱斜率法测过量自由焓之模型参数的研究

研究了色谱测定(σγ/σx)_(x=0)的两种公式——修正的Kikic-Renon公式及Valentin-Guiochon公式,实测了29个二元系的γ_1~∞,分别按两种公式测定(σγ/σx)_(x=0),求取两参数过量自由焓模型参数,进而预测全浓度范围汽液平衡,得到了较为满意的结果.对Valentin-Guiochon公式合理简化,提出了一个较为简便的(σγ/σx)_(x=0) 公式.利用Gmehling等汇编的56个含醇及含水二元系γ_1~∞数据,直接计算该公式的(σγ/σx)_(x=0)之值,进而推算过量自由焓模型参数,并预测汽液平衡.又用气液色谱测定了各种含有极性与非极性组分、挥发与难挥发组分的不同类型43个二元系的γ_1~∞值,按上述方法预测全浓度范围汽液平衡,与文献中已发表的汽液平衡数据比较,结果都符合良好.最后,讨论了三种斜率公式各自的适用范围和两参数过量自由焓模型转化为单参数模型的一般方法.     

无机及分析化学教学探索——以吉布斯自由能为例

以吉布斯自由能变与分析化学部分四大平衡的关系为主线,由点到面,将化学热力学部分与分析化学部分基础理论知识有机的联系起来,启发学生的发散性思维。通过知识点的归纳和整理,让学生学会如何构建自己的知识体系,活学活用基础理论知识。     

Standard Gibbs Energy of Formation of β-Silicon Nitride

Experimental thermochemical data (temperature, pressure) corresponding to the equilibrium conditions between finegrained β-SiC and β-Si₃N₄ for carbon activity a (C) = 1 are presented. Based on these data, the temperature dependence of ΔG°_f(β-Si₃N₄) has been expressed for standard states Si( s ), C( s ), and p(N₂) = 0.1 MPa by the equation ΔA°_f(β-Si₃N₄) = (-995.9 + 0.4547 T/K) kJ mol for T/K ε〈1650; 1968〉.     

含高氮化合物的高燃速CMDB推进剂的能量特性

利用能量计算程序计算了含高氮化合物3,6–双(1–氢–1,2,3,4–四唑–5–氨基)–1,2,4,5–四嗪(BTATz)的复合改性双基(CMDB)推进剂的能量特性,并研究了用3种含能添加剂高氯酸铵(AP)、六硝基六氮杂异伍兹烷(HNIW)、黑索今(RDX)和2种增塑剂1,5–二叠氮基–3–硝基–3–氮杂戊烷(DIANP)及二缩三乙二醇二硝酸酯(TEGDN)分别部分取代BTATz和硝化甘油(NG)后,对含BTATz的CMDB推进剂能量特性的影响规律。结果表明:无论推进剂中是否含铝粉,用BTATz取代CMDB推进剂中的硝化棉(NC)和NG后,将不同程度地降低原推进剂的各能量特性参数;用AP和HNIW部分取代BTATz后,可使BTATz–CMDB推进剂的理论比冲明显提高;用DIANP或TEGDN部分取代推进剂中的NG,各能量特性参数均随其含量增加而减小。     

基于稀溶液模型的标准溶解吉布斯自由能与微分溶解焓互算

采用稀溶液模型建立了微分溶解焓与标准溶解吉布斯自由能的互算方法,并以铁液和镍液的标准溶解吉布斯自由能与微分溶解焓热力学数据验证,根据铝熔体中部分金属元素微分溶解焓计算了铝熔体中金属元素的标准溶解吉布斯自由能与温度关系式,为缺乏标准溶解吉布斯自由能热力学数据的金属熔体反应热力学计算提供了基础.     

用组贡献法预测固体无机盐的标准生成热和吉布斯自由能

开发了组贡献方法用于预测固体无机盐的△Ｈ＾２９８ｆ和△Ｇ＾２９８ｆ。这个方法提供了２３种阴离子，１３６种阳离子和五种配位分子，１２６种阳离子和３种配位分了孤加和性常数以预测△Ｇ＾２９８ｆ。对９３８种固体无机化合物的△Ｈ＾２９８ｆ和６８７种固体无机化合物的△Ｇ＾２９８ｆ进行数据回归分析，△Ｈ２９８ｆ和△Ｇ＾２９８ｆ预测值的平均误差分别为２．５７％和２．６０％，对每个加和性常数的相对误差值也进行了估算     

Chemical Composition Determination at the Bottom Region of a Recovery Boiler Furnace by Direct Minimization of Gibbs Free Energy

An optimization strategy has been applied to describe the chemical composition at the furnace bottom in the Kraft recovery boiler of a pulp production process. The concentrations of each involved chemical species were calculated through an optimization approach, minimizing the Gibbs free energy of the system. Various systems were proposed and tested, assuming different chemical species and phases number. Because serious initialization problems were found at this stage for some of the proposed systems, an optimization heuristic method (PSO) was used for the first approach to the problem. Once the appropriate phases number and chemical species in the system were determined, the initialization problems disappeared and the use of a deterministic optimization method (SQP) became viable. The proposed approach has shown to be satisfactory to reproduce industrial data and also data reported in the open scientific literature.