Thermochemistry of iron chlorides and their positive and negative ions
Thermochemistry of iron chlorides and their positive and negative ions
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DOI：
10.1021/jp953687w
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发表时间：
1996-05-23
影响因子：
--
通讯作者：
Nagel, CJ
中科院分区：
文献类型：
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作者：
Bach, RD;Shobe, DS;Nagel, CJ
对氯化铁FeCl2、FeCl2、FeCl3及其离子FeCl2、FeCl3-及其离子FeCl2、FeCl2、FeCl3-进行了MP2和QCISD(T)计算，其中双Zeta基组和三Zeta基组分别加入了多组扩散函数和极化函数。预测了FeCl2-&Gt、FeCl2-Gt、FeCl3-GtFeCl2+Cl3在298.15 K时的离解热分别为82.5千卡/摩尔、109.6千卡/克分子和59.6千卡/克分子。在298.15 K时，这些物种在气相中的生成热分别为+45.3千卡/摩尔、-35.8千卡/摩尔和-66.8千卡/摩尔。计算的FeCl生成热比JANAF表中所报道的+60.0(+/-20.0)千卡/摩尔的估计值低15千卡/摩尔，但与最近的实验测定结果(49.5+/-1.6千卡/摩尔)符合得相当好。计算得到FeCl的电离势为7.89 eV，FeCl2的电离势为10.10 eV。电子亲和能FeCl1.54 eV，FeCl2 0.99 eV，FeCl3 3.90 eV。比较FeCln、FeCln+和FeCln中的键离解热-发现铁更倾向于以+2的氧化态存在(以FeCl2、FeCl3+或FeCl3-的形式存在)；当比较氯化铁的IP和EAs时，也可以看到这种偏好。我们还用密度泛函理论的B3LYP版本计算了氯化铁物种的离解能、IPs和EAs。与高水平从头计算结果的比较表明，带目标基组的密度泛函理论对这些物种的计算精度为5-10千卡/摩尔。
The iron chlorides FeCl, FeCl2, and FeCl3 and their ions FeCl+, FeCl2+, FeCl-, FeCl2-, and FeCl3- were investigated using MP2 and QCISD(T) calculations with double- and triple-zeta basis sets augmented with multiple sets of diffuse and polarization functions. The dissociation enthalpies for FeCl --> Fe + Cl, FeCl2 --> FeCl + Cl, and FeCl3 --> FeCl2 + Cl are predicted to be 82.5, 109.6, and 59.6 kcal/mol at 298.15 K, respectively. The calculated heats of formation of these species in the gas phase at 298.15 K are +45.3 kcal/mol for FeCl, -35.8 kcal/mol for FeCl2, and -66.8 kcal/mol for FeCl3. The calculated heat of formation of FeCl is 15 kcal/mol lower than the estimated value of +60.0 (+/-20.0) kcal/mol reported in the JANAF tables, but is in reasonably good agreement with a recent experimental determination (49.5 +/- 1.6 kcal/mol). The calculated ionization potential of FeCl is 7.89 eV and that of FeCl2 is 10.10 eV. The electron affinities are 1.54 eV for FeCl, 0.99 eV for FeCl2, and 3.90 eV for FeCl3. Comparison of the bond dissociation enthalpies in FeCln, FeCln+, and FeCln- reveals a preference for iron to exist in the +2 oxidation state (as FeCl2, FeCl+, or FeCl3-); this preference is also seen when comparing IPs and the EAs of the iron chlorides. We also evaluated the dissociation energies, IPs and EAs of the iron chloride species using the B3LYP version of density functional theory. Comparison to the high-level ab initio results shows that density functional theory with the targe basis set is accurate to 5-10 kcal/mol for these species.