Clumped-isotope signatures at equilibrium of CH4, NH3, H2O, H2S and SO2

	Clumped-isotope signatures at equilibrium of CH4, NH3, H2O, H2S and SO2
	Qi Liu; Yun Liu
	2016
发表期刊	Geochimica et Cosmochimica Acta
卷号	175 期号:2 页码:252-270
摘要	High precision Delta(i) values at equilibrium determined by theoretical methods are imperatively needed as references for the development of new clumped-isotope thermometers (or tracers). In this study, quantum chemistry methods with corrections beyond the harmonic approximation are used to obtain the clumped-isotope signatures at equilibrium of several gas-phase molecules (i.e., CH4, NH3, H2O, H2S, and SO2). Here, we consider as many corrections to the traditional Bigeleisen-Mayer equation as possible to obtain accurate Delta(i) values at equilibrium and their temperature dependences. The corrections include anharmonic correction for zero-point energy, anharmonic correction for vibrational excited states, vibration-rotation coupling correction for zero-point energy, vibration-rotation coupling correction for vibrational excited states, quantum mechanical correction to rotation, and centrifugal distortion correction, which are important for theoretical understanding of clumped-isotope signals. Specifically, molecular constants are calculated via second-order perturbative analysis at the MP2/aug-cc-pVTZ level. The CCSD/6-311+G(3df,3pd) and CCSD/aug-cc-pVTZ levels are further employed to ensure the precision of harmonic frequencies of methane. For methane, a polynomial fit of Delta 13CH3D values over the temperature range of from 273.15 to 1000 K is obtained: Delta 13CH3D = 0.00255 (1000/T)(4) = 0.11639 (1000/T)(3) +1.01364 (1000/T)(2) =0.43627 (1000/T) Our results are slightly different from previous theoretical calculations, and may serve as new anchors for calibrating experimental observations.
学科领域	矿床地球化学
收录类别	SCI
语种	英语
文献类型	期刊论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/6083
专题	矿床地球化学国家重点实验室_矿床地球化学国家重点实验室_期刊论文
推荐引用方式 GB/T 7714	Qi Liu,Yun Liu. Clumped-isotope signatures at equilibrium of CH4, NH3, H2O, H2S and SO2[J]. Geochimica et Cosmochimica Acta,2016,175(2):252-270.
APA	Qi Liu,&Yun Liu.(2016).Clumped-isotope signatures at equilibrium of CH4, NH3, H2O, H2S and SO2.Geochimica et Cosmochimica Acta,175(2),252-270.
MLA	Qi Liu,et al."Clumped-isotope signatures at equilibrium of CH4, NH3, H2O, H2S and SO2".Geochimica et Cosmochimica Acta 175.2(2016):252-270.

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