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Thermal, spectroscopic and electrical properties of lead pyrophosphate glass prepared by melt quenching have been examined.
A model based on the structural disproportionation of the P2O
7
4−
ions has been proposed and is shown to consistently explain all the observations. The equilibrium of various anionic species
has been discussed on the basis of their electronegativities which are in turn related to their basicities.
Communication No. 129 from the Materials Research Centre 相似文献
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Egbert Hahn Johanna Fruwert und Heinz Böhlig 《Monatshefte für Chemie / Chemical Monthly》1984,115(8-9):935-942
Comparable force fields for HCOO–, HFCO, HClCO and HDCO have been calculated on the basis of internal coordinates. Linear relations between (i) the carbonyl bond order and the carbonyl stretching force constant, (ii) the sum of the three in-plane bending force constants and the hydrogen out-of-plane force constantf
, (iii) a combination of orbital electronegativities andf
, have been obtained. The observed in-plane vibrational frequencies have been calculated with an average error of 6.3 cm–1 or 0.4%. 相似文献
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Correlations between 19F NMR chemical shifts (Φ) in fluorohalohydrocarbons and enthalpies of formation, bond dissociation energies, group contribution to enthalpies of formation and enthalpies of formation of free radicals are presented. A good correlation between these properties has been found with the square root of Φ. A relationship between fluorine chemical shifts and group electronegativities is also discussed. 相似文献
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一种价态元素电负性的新标度 总被引:2,自引:0,他引:2
本文利用原子的价层轨道能、共价半径和有效主量子数为主要参数,以静电力为基础计算了价态元素电负性,本文计算了78种元素常见价态的电负性,由此,产生了一套价态元素电负性的新标度,其计算公式为:Xy=0.070n*(-∑Ei)1/2/rc2+0.820式中Ei为原子的价层轨道能,rc为原子的共价半径,n*为有效主量子数。该标度不但容易理解和计算,而且标度值比已有的文献值更接近传统的鲍林电负性值。此外,该标度值的相对大小还能反映配合物的稳定性,过渡金属收缩和镧系元素收缩等性质。 相似文献
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Hermes F. de Souza Paulo H. Guadagnini Rogrio Custodio John D. Goddard 《Journal of computational chemistry》2000,21(13):1119-1131
Proton affinities for hydrides of formula $\mathrm{AH}^{-}_{n-1}$ containing the elements A from the second to the fifth period of the periodic table and groups 14 to 17 are predicted at the Hartree–Fock, MP2 and B3LYP levels of theory employing both core potential basis sets and the 3‐21G basis set. The core potential methods perform well when compared with all electron calculations using the 3‐21++G** basis set. The proton affinities of the hydrides containing elements from groups 15 and 16 of the periodic table are more accurate than those with elements from groups 14 and 17. A cancellation of errors appears to occur more completely if the protonated and nonprotonated molecules contain both bond and lone pairs before and after the protonation reaction. Proton affinities correlate nearly linearly with the atomic charges on the hydrogen atoms when these charges are determined by the generalized atomic polar tensor (GAPT) method. This tendency can be associated, in principle, with the group electronegativities as introduced by Iczkowski and Margrave. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 1119–1131, 2000 相似文献
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建立材料的折射率和某些原子参数之间的定性关系并以一些氧化物晶体的折射率实验数据作了验证,文中定义了参数P=r^-1(r^ ΔχD),式中Δχ是材料中半径为r^ 的阳离子和半径为r^-的阴离子之间的电负性差,D是本文引进的描述离子质量差异效应的因子。文中从理论上同时也从具体实验数据的讨论上证明了材料的折射率是参数P的减函数,这个关系对光学材料的研究有帮助。 相似文献
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