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The varying nature of fluorine-oxygen bonds

机译:氟-氧键的变化性质

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摘要

The singles and doubles coupled-cluster method that includes a per-turbational estimate of the effects of connected triple excitations, CCSD(T), together with a triple zeta double polarized (TZ2P) one-particle basis set is used to determine the geometries, harmonic frequencies, infrared intensities, and dipole moments of HOF, F_2O, HOOF, FOOF, ClOOF. Agreement with experiment is very good, with the exception that the currently accepted experimental assignment of the symmetric and antisymmetric O-F stretches in FOOF is shown to be reversed (and to be consistent with an earlier experimental study). Very accurate heats of formation of HOOF, FOOF and ClOOF are also computed using the CCSD(T) method in conjunction with large atomic natural orbital basis sets. The F-O bond distances, quadratic force constants, bond energies, and fluorine and oxygen atomic charges from the above five molecules and six previously studied molecules (FONO_2, trans-FONO, cis-FONO, FOCl, FOBr and FON) are compared and used to deduce a simple model of F-O bonding. The unusual relationship between the F-O bond distance and quadratic force constant shows that F-O bonding is a function of at least three eifects, which are degree of covalent character, degree of ionic character, and extent of lone electron-pair repulsions. All of the data are qualitatively consistent with this simple model. The bonding in cis-FONO is even more complicated, involving also dispersion interactions between fluorine and the terminal oxygen. It is suggested that the general importance of lone pair repulsions in F-O bonding and the additional importance of intra-molecular dispersion interactions explains why many density functionals have difficulty in describing the geometry of cis-FONO.
机译:单打和双打耦合群集方法包括确定连接的三重激发效应的逐扰估计CCSD(T)以及三重zeta双极化(TZ2P)单粒子基础集,用于确定几何形状, HOF,F_2O,HOOF,FOOF,ClOOF的谐波频率,红外强度和偶极矩。与实验的一致性非常好,不同的是,目前公认的FOOF中对称和反对称O-F延伸的实验分配是相反的(并且与早期的实验研究一致)。还使用CCSD(T)方法结合大型原子自然轨道基础集计算了HOOF,FOOF和ClOOF形成的非常精确的热量。比较以上五个分子和六个先前研究的分子(FONO_2,反式FONO,顺式-FONO,FOCl,FOBr和FON)的FO键距离,二次力常数,键能以及氟和氧原子电荷,并将其用于推导出一个简单的FO键合模型。 F-O键距离与二次力常数之间的异常关系表明,F-O键是至少三个效应的函数,这些效应是共价特征度,离子特征度和孤电子对排斥的程度。所有数据在质量上都与此简单模型一致。顺式-FONO中的键甚至更复杂,还涉及氟与末端氧之间的分散相互作用。建议孤对排斥在F-O键中的一般重要性和分子内分散相互作用的其他重要性解释了为什么许多密度泛函很难描述顺式-FONO的几何形状。

著录项

  • 来源
    《Molecular physics》 |1996年第5期|p.1359-1372|共14页
  • 作者单位

    MS230-3, NASA Ames Research Center, Moffett Field, California 94035-1000, USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 分子物理学;
  • 关键词

  • 入库时间 2022-08-18 01:08:10

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