Two States Are Not Enough: Quantitative Evaluation of the Valence‐Bond Intramolecular Charge‐Transfer Model and Its Use in Predicting Bond Length Alternation Effects

The structural weights of the canonical resonance contributors used in the Two‐state valence‐bond charge‐transfer model, neutral (N, R1) and ionic (VB‐CT, R2), to the ground states and excited states of a series of linear dipolar intramolecular charge‐transfer chromophores containing a buta‐1,3‐dien‐1,4‐diyl bridge have been computed by using the block‐localized wavefunction (BLW) method at the B3LYP/6‐311+G(d) level to provide the first quantitative assessment of this simple model. Ground‐ and excited‐state analysis reveals surprisingly low ground‐state structural weights for the VB‐CT resonance form using either this Two‐state model or an expanded Ten‐state model. The VB‐CT state is found to be more prominent in the excited state. Individual resonance forms were structurally optimized to understand the origins of the bond length alternation (BLA) of the bridging unit. Using a Wheland energy‐based weighting scheme, the weighted average of the optimized bond lengths with the Two‐state model was unable to reproduce the BLA features with values 0.04 to 0.02 Å too large compared to the fully delocalized (FD) structure (BLW: ca. ?0.13 to ?0.07 Å, FD: ca. ?0.09 to ?0.05 Å). Instead, an expanded Ten‐state model fit the BLA values of the FD structure to within only 0.001 Å of FD.     

计算饱和醇异构体标准生成焓的新方法

基于极性叠加原理,在成功设计烷烃异构体和多氯代烷烃生成焓计算新方法的基础上,设计了一种计算多元醇异构体生成焓的新方法,并合理地假定任一异构体的原子化焓等于三种键(C-C、C-H和C-O-H键)的键能、极性叠加能项以及氢键能项的加和.用这一模型拟合24种原子化焓数据,得到了标准生成焓的估算公式.为了检验预测的精确性,又设计了一种预测方法,使用在排除被预测的化合物条件下回归得到的参数,预测该化合物的生成焓.按这种方法,预测了24种异构体的生成焓.通过该5参数预测的相对于实验值的各种误差(平均绝对误差、均方根误差和最大绝对误差)不仅比7参数的基团法预测的对应误差小得多,而且比相应实验数据的误差还要小.与键加和法比较,该方法的模型包含了极性叠加能和氢键能量,该两项代表了主要的非键相互作用能,表征了不同异构体的结构差异,并大大减少了参数.     

Modal part analysis of slosh of the liquid in a cylindrical container in the case of small bond number

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Degradation of Amino-(3-methoxyphenyl)methanephosphonic Acid by Alternaria sp

Alternaria sp. isolated from the surface of carrot ( Daucus carota ) seeds appeared to be able to degrade amino-(4-methoxyphenyl)-methanephosphonic acid using it as a sole source of carbon, nitrogen, and phosphorus for growth.     

Correlation between thermal conductivity and bond length alternation in carbon nanotubes: A combined reverse nonequilibrium molecular dynamics—Crystal orbital analysis

The thermal conductivity (λ) of carbon nanotubes (CNTs) with chirality indices (5,0), (10,0), (5,5), and (10,10) has been studied by reverse nonequilibrium molecular dynamics (RNEMD) simulations as a function of different bond length alternation patterns (Δr_i). The Δr_i dependence of the bond force constant (k_rx) in the molecular dynamics force field has been modeled with the help of an electronic band structure approach. These calculations show that the Δr_i dependence of k_rx in tubes with not too small a diameter can be mapped by a simple linear bond length–bond order correlation. A bond length alternation with an overall reduction in the length of the nanotube causes an enhancement of λ, whereas an alternation scheme leading to an elongation of the tube is coupled to a decrease of the thermal conductivity. This effect is more pronounced in carbon nanotubes with larger diameters. The formation of a polyene‐like structure in the direction of the longitudinal axis has a negligible influence on λ. A comparative analysis of the RNEMD and crystal orbital results indicates that Δr_i‐dependent modifications of λ and the electrical conductivity are uncorrelated. This behavior is in‐line with a heat transfer that is not carried by electrons. Modifications of λ as a function of the bond alternation in the (10,10) nanotube are explained with the help of power spectra, which provide access to the density of vibrational states. We have suggested longitudinal low‐energy modes in the spectra that might be responsible for the Δr_i dependence of λ. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Bond pricing under a Markovian regime-switching jump-augmented Vasicek model via stochastic flows

In this article, we shall explore the state of art of stochastic flows to derive an exponential affine form of the bond price when the short rate process is governed by a Markovian regime-switching jump-diffusion version of the Vasicek model. We provide the flexibility that the market parameters, including the mean-reversion level, the volatility rate and the intensity of the jump component switch over time according to a continuous-time, finite-state Markov chain. The states of the chain may be interpreted as different states of an economy or different stages of a business cycle. We shall provide a representation for the exponential affine form of the bond price in terms of fundamental matrix solutions of linear matrix differential equations.     

Paradigms and Paradoxes: Electronegativity and Bond Energies—Living Legacies of Linus and Lee

In this paper we will discuss Pauling's classic Eq. (1) that relates bond energies, "D," and electronegativities, "x." Recast to be applicable to enthalpies of formation and reaction, we apply it to the study of hydrogenolysis reactions of dienes, diynes, and alkanes, halogenolysis reactions (with chlorine, bromine, and iodine) and metathetical reactions of organosulfur species (sulfides, sulfoxides, and sulfones). It is with great regret that this equation is found wanting.     

Vergleichbare Kraftfelder vieratomiger Formylverbindungen

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%.