Computational Studies of Isotopic Fractionation of B, O, S, Cu and Mo

John A.从理论上研究了硼（B）、氧（O）、硫（S）、铜（Cu）、钼（Mo）等地球化学重要元素的TOSSELLISotopic分馏过程。这些研究将采用最先进的量子化学方法，并将仔细评估计算和实验的一致性，重点是不同同位素异构体的振动频率比和同位素分馏平衡的现有实验数据。我们将采用超分子或纳米团簇模型的水的物种和测试收敛的量子化学方法的准确性和集群的大小。涉及这些物质的化学反应的能量也将被计算，因为化学平衡必须与同位素平衡一起沿着考虑，以确定同位素分馏的程度。我们最近在计算和解释B和Mo同位素分馏方面的成功（Liu和Tossell，2005; Tossell，2005 c）将被用作拟议工作的基础。我们还将把我们的研究扩展到其他元素（O、S和Cu）以及超临界状态下的高T和P条件，就像我们最近对辛酸的低聚反应所做的那样（Tossell，2005 a）。我们还将研究同位素分馏的非均相过程中，涉及吸附到碳酸盐矿物表面和硼硅酸盐矿物与含硼玻璃或熔体的相互作用的硼酸盐物种。对于每个元素考虑，我们将尝试半定量地解释同位素分馏平衡使用键强度参数或通过与其他计算的属性，如NMR shift.Intellectual优点：更准确的同位素分馏平衡常数和反应平衡常数将被计算和分馏过程中所涉及的化学物种的身份将被澄清。有关这些过程的信息也将扩展到新的地球化学制度的T和P和非均质系统。最后，将建立同位素分馏与矿物结构和光谱特性之间的关系。更广泛的影响：计算科学将扩展到地球科学的新领域。地球科学中实验和理论研究相结合的必要性将再次得到证明，稳定同位素地球化学的解释能力将得到提高。研究生和博士后将接受地球化学和计算化学方面的培训。将向该领域的所有研究人员分发计算同位素分馏常数的标准程序，该程序有现成的软件支持。

EAR-0539109John A. TOSSELLIsotopic fractionation processes will be studied theoretically for a number of geochemically important elements, including Boron (B), Oxygen (O), Sulfur (S), Copper (Cu), Molybdenum (Mo). These studies will employ state-of-the-art quantum chemical methods and will carefully assess the agreement of calculation and experiment, focusing both upon the ratios of vibrational frequencies for different isotopomers and the available experimental data on isotopic fractionation equilibria. We will employ supermolecule or nanocluster models for aqueous species and test for convergence in both accuracy of the quantum chemical method and size of the cluster. The energies of chemical reactions involving these species will also be calculated, since chemical equilibria must be considered along with isotopic equilibria to determine the extent of isotopic fractionation. Our recent successes in calculating and interpreting B and Mo isotopic fractionations (Liu and Tossell, 2005; Tossell, 2005c) will be used as foundations for the proposed work. We will also extend our studies both to other elements (O, S and Cu) and to conditions of high T and P, in the supercritical regime, just as we have recently done for the oligomerization reactions of silicic acid (Tossell, 2005a). We will also study isotopic fractionation in heterogeneous processes involving adsorption of borate species onto carbonate mineral surfaces and the interaction of borosilicate minerals with B-containing glasses or melts. For each element considered we will try to semiquantitatively interpret the isotopic fractionation equilibria using bond strength arguments or by correlation with other calculated properties, such as NMR shifts.Intellectual merit: More accurate isotopic fractionation equilibrium constants and reaction equilibrium constants will be calculated and the identity of the chemical species involved in the fractionation processes will be clarified. Information on such processes will also be extended to new geochemical regimes of T and P and to heterogeneous systems. Finally, relationships between isotopic fractionation and mineral structural and spectroscopic properties will be established.Broader impacts: Computational science will be extended into new areas of geosciences. The need for combined experimental and theoretical studies in geosciences will again be demonstrated and the explanatory power of stable isotope geochemistry increased. Graduate students and postdocs will be trained in both geochemistry and computational chemistry. Standard procedures for calculating isotopic fractionation constants, supported by readily available software, will be disseminated to all researchers in the field.