Institute of Chemistry, Laboratory of Molecular Spectroscopy, Loránd Eötvös University, 1518 Budapest 112, P.O. Box 32, Hungary.
Chemistry. 2010 Apr 26;16(16):4826-35. doi: 10.1002/chem.200903252.
A simple and fast, weighted, linear least-squares refinement protocol and code is presented for inverting the information contained in a network of quantum chemically computed 0 K reaction enthalpies. This inversion yields internally consistent 0 K enthalpies of formation for the species of the network. The refinement takes advantage of the fact that the accuracy of computed enthalpies depends strongly on the quantum-chemical protocol employed for their determination. Different protocols suffer from different sources of error; thus, the reaction enthalpies computed by them have "random" residual errors. Since it is much more natural for quantum-chemical energy and enthalpy results, including reaction enthalpies, to be based on the electronic ground states of the atoms and not on the historically preferred elemental states, and since these two possible protocols can be converted into each other straightforwardly, it is proposed that first-principles thermochemistry should employ the ground electronic states of atoms. In this scheme, called atom-based thermochemistry (AT), the enthalpy of formation of a gaseous compound corresponds simply to the total atomization energy of the species; it is always positive, and it reflects the bonding strength within the molecule. The inversion protocol developed and based on AT is termed NEAT, which represents the fact that the protocol proceeds from a network of computed reaction enthalpies toward atom-based thermochemistry, most directly to atom-based enthalpies of formation. After assembling a database that consisted of 361 ab initio reactions and reaction enthalpies involving 188 species, collected from 31 literature sources, the following dependable 0 K atom-based enthalpies of formation, Delta(f)${H{{{\rm AT}\hfill \atop 0\hfill}}}$, all in kJ mol(-1), have been obtained by means of NEAT: H(2)=432.07(0), CH=334.61(15), NH=327.69(25), OH=425.93(21), HF=566.13(31), CO=1072.08(28), O(2)=493.51(34), CH(2)=752.40(21), H(2)O=918.05(20), HO(2)=694.53(32), CO(2)=1597.77(40), CH(3)=1209.64(29), NH(3)=1157.44(33), C(2)H(2)=1625.78(40), and CH(4)=1641.68(40), in which the uncertainty values given in parentheses represent 95 % confidence intervals. The average deviation of these values from the well-established active thermochemical tables (ATcT) values is a mere 0.25 kJ mol(-1), with a maximum deviation of 0.7 kJ mol(-1). This shows that the use of a large number of ab initio reaction enthalpies within a NEAT-type protocol has considerable advantages over the sequential utilization of the ab initio information.
提出了一种简单快速的加权线性最小二乘精修方案和代码，用于反转网络量子化学计算的 0 K 反应焓中包含的信息。这种反演为网络中的物种生成了内部一致的 0 K 生成焓。精修利用了这样一个事实，即计算焓的准确性强烈依赖于用于确定它们的量子化学协议。不同的协议有不同的误差源；因此，它们计算的反应焓有“随机”残余误差。由于量子化学能量和焓的结果，包括反应焓，更自然地基于原子的电子基态，而不是历史上首选的元素态，并且由于这两种可能的协议可以直接相互转换，因此建议第一性原理热化学应该采用原子的基态电子。在这种称为基于原子的热化学 (AT) 的方案中，气态化合物的生成焓简单地对应于物种的总原子化能；它总是正的，反映了分子内的键合强度。基于 AT 开发并基于此的反演协议称为 NEAT，它代表了协议从计算反应焓的网络向基于原子的热化学、最直接地向基于原子的生成焓推进的事实。在收集了 31 个文献来源的 361 个从头算反应和反应焓后，组装了一个数据库，以下可靠的 0 K 基于原子的生成焓，Delta(f)${H{{{\rm AT}\hfill \atop 0\hfill}}}$，均以 kJ mol(-1)为单位，已通过 NEAT 获得：H(2)=432.07(0)，CH=334.61(15)，NH=327.69(25)，OH=425.93(21)，HF=566.13(31)，CO=1072.08(28)，O(2)=493.51(34)，CH(2)=752.40(21)，H(2)O=918.05(20)，HO(2)=694.53(32)，CO(2)=1597.77(40)，CH(3)=1209.64(29)，NH(3)=1157.44(33)，C(2)H(2)=1625.78(40)和 CH(4)=1641.68(40)，括号中的不确定性值表示 95%置信区间。这些值与经过良好验证的活性热化学表 (ATcT) 值的平均偏差仅为 0.25 kJ mol(-1)，最大偏差为 0.7 kJ mol(-1)。这表明在 NEAT 型协议中使用大量从头算反应焓相对于顺序使用从头算信息具有相当大的优势。
