Entropies and Heat Capacities of Gaseous Selenium Molecules Sen (n = 5 ... 12)

Thermodynamic functions are calculated for gaseous Se8 molecules from spectroscopic and structural data and listed for temperatures up to 3000 K. Entropy (S°) and heat capacity (Cp0) data for Sen molecules (n = 5, 6, 7, 9, 10, 11, 12) are obtained from linear relationships between both S0 and Cp0 and ring size n which are derived from the corresponding values of Se2 and Se8

Justifying additive-noise-model based causal discovery via algorithmic information theory

A recent method for causal discovery is in many cases able to infer whether X causes Y or Y causes X for just two observed variables X and Y. It is based on the observation that there exist (non-Gaussian) joint distributions P(X,Y) for which Y may be written as a function of X up to an additive noise term that is independent of X and no such model exists from Y to X. Whenever this is the case, one prefers the causal model X--> Y. Here we justify this method by showing that the causal hypothesis Y--> X is unlikely because it requires a specific tuning between P(Y) and P(X|Y) to generate a distribution that admits an additive noise model from X to Y. To quantify the amount of tuning required we derive lower bounds on the algorithmic information shared by P(Y) and P(X|Y). This way, our justification is consistent with recent approaches for using algorithmic information theory for causal reasoning. We extend this principle to the case where P(X,Y) almost admits an additive noise model. Our results suggest that the above conclusion is more reliable if the complexity of P(Y) is high.Comment: 17 pages, 1 Figur

Information-theoretic inference of common ancestors

A directed acyclic graph (DAG) partially represents the conditional independence structure among observations of a system if the local Markov condition holds, that is, if every variable is independent of its non-descendants given its parents. In general, there is a whole class of DAGs that represents a given set of conditional independence relations. We are interested in properties of this class that can be derived from observations of a subsystem only. To this end, we prove an information theoretic inequality that allows for the inference of common ancestors of observed parts in any DAG representing some unknown larger system. More explicitly, we show that a large amount of dependence in terms of mutual information among the observations implies the existence of a common ancestor that distributes this information. Within the causal interpretation of DAGs our result can be seen as a quantitative extension of Reichenbach's Principle of Common Cause to more than two variables. Our conclusions are valid also for non-probabilistic observations such as binary strings, since we state the proof for an axiomatized notion of mutual information that includes the stochastic as well as the algorithmic version.Comment: 18 pages, 4 figure

Low Temperature Raman Spectra of Dichlorosulfane (SC12), Tetrachlorosulfurane (SC14), Dichlorodisulfane (S2C12) and Dichlorodiselane (Se2Cl2) [1]

The Raman spectrum of commercial "sulfur dichloride" shows strong lines due to SCl2 and S2Cl2 and weak Cl2 lines at 25 °C, but strong SCl2 and SCl4 signals at -100 °C (the latter are superimposed on the S2Cl2 lines). Thus, the intense Raman effect of SCl4 can be used to detect small amounts of chlorine in SCl2 . Mixtures of SCl2 and Cl2 (1:15) yield the Raman spectrum of SCl4 at -140 °C, while at 25 °C not trace of this compound can be detected. The spectra of SCl4 and α-SeCl4 are quite different, indicating different molecular and/or crystal structures, although ECl3 + ions (E = S, Se) are present in both cases. While Se2Cl2 dimerizes reversibly below -50 °C, S2Cl2 neither dimerizes nor isomerizes on cooling. The S2Cl2 dimer is characterized by a Raman line at 215 cm-1 the intensity of which was used to calculate an enthalpy of dimerization as of -17 kJ/mol

Justifying Information-Geometric Causal Inference

Information Geometric Causal Inference (IGCI) is a new approach to distinguish between cause and effect for two variables. It is based on an independence assumption between input distribution and causal mechanism that can be phrased in terms of orthogonality in information space. We describe two intuitive reinterpretations of this approach that makes IGCI more accessible to a broader audience. Moreover, we show that the described independence is related to the hypothesis that unsupervised learning and semi-supervised learning only works for predicting the cause from the effect and not vice versa.Comment: 3 Figure

Barrier to Rotation about Sulfur-Sulfur Bonds in Homocyclic Sulfur Molecules

It is shown that the distances (d) of the 19 longest bonds in 9 homocyclic sulfur rings of type Sn (n = 6-20) depend on the torsional angles (τ) which vary between 0° and 140°. The function d = f(τ) is smallest for τ = 90-100° and largest for τ = 0°; the corresponding bond distance variation amounts to 13 pm or 6%. The height of the torsional cis-barrier is estimated from the enthalpy of formation of gaseous S7 as equal to or smaller than 24 kJ/mol

Vibrational Spectra and Force Constants of Tetrasulfurtetranitride, S4N4 [1]

Infrared and Raman spectra of solid and dissolved S414N4 and of solid S415N4 have been recorded and assigned in accordance with the molecular point group D2d. 22 of the 28 fundamental vibrations of both molecules have been identified and used to calculate force constants applying a modified Urey-Bradley force field with 9 independent constants. Good agreement between observed and calculated wavenumbers was obtained, and both Urey-Bradley and valence force constants are given. The results indicate that-S4N4 basically contains eight SN single bonds and two extremely weak SS bonds

The role of polysulfide dianions and radical anions in the chemical, physical and biological sciences, including sulfur-based batteries

The well-known tendency of sulfur to catenate is exemplified by an extensive series of polysulfide dianions [Sn]2− (n = 2–9) and related radical monoanions [Sn]˙−. The dianions can be isolated as crystalline salts with appropriate cations and structurally and spectroscopically characterized. Although the smaller radical monoanions may be stabilized in zeolitic matrices, they are usually formed in solution via disproportionation or partial dissociation of the dianions as well as by electrochemical reduction of elemental sulfur. An understanding of the fundamental chemistry of these homoatomic species is key to unravelling their behaviour in a broad variety of chemical environments. This review will critically evaluate the techniques used to characterize polysulfide dianions and radical anions both in solution and in the solid state, i.e. Raman, UV-visible, EPR, NMR and X-ray absorption spectroscopy, X-ray crystallography, mass spectrometry, chromatography and high-level quantum-chemical calculations. This is followed by a discussion of recent advances in areas in which these anionic sulfur species play a crucial role, viz. alkali-metal–sulfur batteries, organic syntheses, biological chemistry, geochemical processes including metal transport, coordination complexes, atmospheric chemistry and materials science.TU Berlin, Open-Access-Mittel - 201