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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Heats of Formation of Alkali Metal and Alkaline Earth Metal Oxides and Hydroxides: Surprisingly Demanding Targets for High-Level ab Initio Procedures
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Heats of Formation of Alkali Metal and Alkaline Earth Metal Oxides and Hydroxides: Surprisingly Demanding Targets for High-Level ab Initio Procedures

机译：碱金属和碱土金属氧化物和氢氧化物的形成热：令人惊讶地要求高水平从头算程序的目标

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High-level ab initio calculations, including variants of the W_n and G3 procedures, have been used to determine the structures and heats of formation of the alkali metal and alkaline earth metal oxides and hydroxides (M_2O, MOH: M = Li, Na, and K; MO, M(OH)_2: M = Be, Mg, and Ca). Our best structures were obtained at the CCSD(T)(riv,rv)aug'-cc-pWCVQZ level and are in uniformly close agreement with available experimental data, with a mean absolute deviation from experimental metal-oxygen bond lengths of just 0.007 A. Structures obtained with CCSD(T)/cc-pWCVQZ, B3-LYP/cc-pVTZ, B3-LYP/6-31G(2df,p), and MP2 (full)/6-311+G(3df,2p) are also in good agreement with experiment. Zero-point vibrational energies and enthalpy temperature corrections are found to be relatively insensitive to the various procedures employed. However, the heats of formation for these molecules are challenging targets for high-level ab initio procedures. In the Wn-type procedures, it is found that expanding the correlation space on the metal atoms from the normal relaxed valence (rv) (or frozen-core) specification to relaxed inner valence (riv) requires the use of newly developed core-valence basis sets (cc-pWCVnZ) in the extrapolation calculations to obtain reliable results. Our best calculated heats of formation (△H_(f 298)) come from a procedure designated W2C//ACQ, while G3[CC](dir,full) is the best of the G3-type procedures. Recommended △H_(f 298) values, weighted toward the W2C//ACQ results, are -157±5 (Li_2O), -25±5 (Na_2O), -60±5 (K_2O), +130±12 (BeO), +142±10 (MgO), +26±17 (CaO), -239±5(LiOH), -189±5(NaOH), -223±5 (KOH), -632±7 (Be(OH)_2), -547±5 (Mg(OH)_2), and -604±19 (Ca(OH)_2) kJ mol~(-1).
机译：包括W_n和G3程序的变体在内的高级从头算算已被用来确定碱金属和碱土金属氧化物和氢氧化物的结构和形成热（M_2O，MOH：M = Li，Na和K; MO，M（OH）_2：M = Be，Mg和Ca）。我们的最佳结构是在CCSD（T）（riv，rv）aug'-cc-pWCVQZ水平上获得的，与可用的实验数据一致一致，与实验金属-氧键长度的平均绝对偏差仅为0.007 A用CCSD（T）/ cc-pWCVQZ，B3-LYP / cc-pVTZ，B3-LYP / 6-31G（2df，p）和MP2（full）/ 6-311 + G（3df，2p）获得的结构与实验也很吻合发现零点振动能和焓温度校正对所采用的各种程序相对不敏感。然而，这些分子的形成热是高水平从头算程序的挑战性目标。在Wn型过程中，发现将金属原子上的相关空间从正常弛豫价（rv）（或冻结核）规格扩展到弛豫内价（riv）需要使用新开发的核价外推计算中的基数集（cc-pWCVnZ），以获得可靠的结果。我们计算出的最佳形成热（△H_（f 298））来自名为W2C // ACQ的程序，而G3 [CC]（dir，full）是G3型程序中最好的。推荐的△H_（f 298）值朝W2C // ACQ结果加权，为-157±5（Li_2O），-25±5（Na_2O），-60±5（K_2O），+ 130±12（BeO） ，+ 142±10（MgO），+ 26±17（CaO），-239±5（LiOH），-189±5（NaOH），-223±5（KOH），-632±7（Be（OH） _2），-547±5（Mg（OH）_2）和-604±19（Ca（OH）_2）kJ mol〜（-1）。

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