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

EAR-0539109约翰·A·TOSSELL将从理论上研究一些重要的地球化学元素，包括硼(B)、氧(O)、硫(S)、铜(Cu)、钼(Mo)的同位分馏过程。这些研究将使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率和关于同位素分馏平衡的现有实验数据。我们将使用超分子或纳米团簇模型来研究含水物种，并测试量子化学方法的准确性和团簇大小的收敛。还将计算涉及这些物种的化学反应的能量，因为必须将化学平衡与同位素平衡一起考虑，以确定同位素分馏的程度。我们最近在计算和解释B和Mo同位素分馏方面取得的成功(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和铜)以及超临界条件下的高T和P条件，就像我们最近对硅酸齐聚反应所做的那样(Tossell，2005a)。我们还将研究非均相过程中的同位素分馏，包括硼酸盐物种在碳酸盐矿物表面的吸附以及硼硅酸盐矿物与含硼玻璃或熔体的相互作用。对于所考虑的每种元素，我们将尝试使用键强度论点或通过与其他计算的性质(如核磁共振位移)的关联来半定量地解释同位素分馏平衡。智力优势：将计算出更准确的同位素分馏平衡常数和反应平衡常数，并将澄清分馏过程中涉及的化学物种的身份。关于这种过程的信息还将扩展到T和P的新的地球化学体系和非均质系统。最后，将建立同位素分馏与矿物结构和光谱性质之间的关系。广泛的影响：计算科学将扩展到地学的新领域。地球科学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增强。研究生和博士后将接受地球化学和计算化学方面的培训。在现成软件的支持下，计算同位素分馏常数的标准程序将分发给该领域的所有研究人员。

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.