Relativistic contribution: an electronic explanation to the thermal disproportionation of PtF5

2017 ◽  
Author(s):  
Robson de Farias
Keyword(s):  
Experimental Data ◽  
Gaseous Phase ◽  
Thermal Instability ◽  
Solid Phase ◽  
Electronic Configuration ◽  
Thermochemical Study ◽  
Energy Diagram ◽  
Unpaired Electrons

<div> <p>In the present work, is performed a computational thermochemical study of platinum tetrafluoride (PtF<sub>4</sub>) and platinum pentafluoride (PtF<sub>5</sub>). The results are compared to those previously [1] obtained to PtF<sub>6</sub> as well as experimental data. Is concluded that in gaseous phase PtF<sub>4</sub> and PtF<sub>5</sub> retain their structures and number of unpaired electrons exhibited in the solid phase. Furthermore, is proposed that the generally accepted t<sub>2g</sub><sup>5</sup>e<sub>g</sub><sup>0 </sup>configuration to Pt<sup>5+</sup> is not correct. Based on the calculated results, an energy diagram is proposed to PtF<sub>5</sub>, which explain why, upon heating, platinum pentafluoride disproportionates readily [7]: 2PtF<sub>5</sub> → PtF<sub>4</sub> + PtF<sub>6</sub>, providing a clear, elegant and straightforward explanation to the thermal instability of PtF<sub>5</sub> as consequence of the electronic configuration. </p> </div>

Relativistic contribution: an electronic explanation to the thermal disproportionation of PtF5

2017 ◽  
Author(s):  
Robson de Farias
Keyword(s):  
Experimental Data ◽  
Gaseous Phase ◽  
Thermal Instability ◽  
Solid Phase ◽  
Electronic Configuration ◽  
Thermochemical Study ◽  
Energy Diagram ◽  
Unpaired Electrons

<div> <p>In the present work, is performed a computational thermochemical study of platinum tetrafluoride (PtF<sub>4</sub>) and platinum pentafluoride (PtF<sub>5</sub>). The results are compared to those previously [1] obtained to PtF<sub>6</sub> as well as experimental data. Is concluded that in gaseous phase PtF<sub>4</sub> and PtF<sub>5</sub> retain their structures and number of unpaired electrons exhibited in the solid phase. Furthermore, is proposed that the generally accepted t<sub>2g</sub><sup>5</sup>e<sub>g</sub><sup>0 </sup>configuration to Pt<sup>5+</sup> is not correct. Based on the calculated results, an energy diagram is proposed to PtF<sub>5</sub>, which explain why, upon heating, platinum pentafluoride disproportionates readily [7]: 2PtF<sub>5</sub> → PtF<sub>4</sub> + PtF<sub>6</sub>, providing a clear, elegant and straightforward explanation to the thermal instability of PtF<sub>5</sub> as consequence of the electronic configuration. </p> </div>

Modeling and Simulation of a Pilot-Scale Bubbling Fluidized Bed Gasifier for the Gasification of High Ash Indian Coal Using Eulerian Granular Approach

2016 ◽  
Vol 14 (1) ◽  
pp. 417-431 ◽  
Author(s):  
G. K. Singh ◽  
B. Mohanty ◽  
P. Mondal ◽  
P. Chavan ◽  
S. Datta
Keyword(s):  
Experimental Data ◽  
Modeling And Simulation ◽  
Fluidized Bed ◽  
Gaseous Phase ◽  
Solid Phase ◽  
Pilot Scale ◽  
Indian Coal ◽  
Bubbling Fluidized Bed ◽  
Fluidized Bed Gasifier ◽  
Phase Phase

AbstractThe present work deals with modeling and simulation of a pilot-scale bubbling fluidized bed gasifier (BFBG) for the gasification of high ash Indian coal. Taking into account different stages of coal gasification, such as drying, volatilization, gasification and combustion processes, a two-dimensional model with quadrilateral cells is developed using FLUENT 12.0 software. The model incorporates exchange of mass, momentum and energy between gaseous phase (phase 1) and solid phase (phase 2) using Eulerian–Eulerian approach. The solid phase is described by kinetic theory of granular flows. Four heterogeneous and four homogeneous reactions covering six species in gaseous phase (CO, CO2, H2, N2, O2 and H2O) and coal in solid phase are considered for the above process. The kinetics for the homogeneous reactions are described using eddy dissipation model available in FLUENT while that for heterogeneous reactions, a user-defined function (UDF) with Arrhenius kinetics is written in C language. The validation of the above model has been done using experimental data generated in a pilot-scale BFBG at Center Institute of Mining and Fuel Research (CIMFR), Dhanbad, India. The computed exit gas compositions as well as temperature profile inside the gasifier are in good agreement (within an error band of ±10%) with experimental data. The flow behaviors and volume fraction profiles of gas and solid phases in the bed zone and freeboard zone of the gasifier have also been predicted using this model.

Explaining the magnetism of gold

2017 ◽  
Author(s):  
Robson de Farias
Keyword(s):  
Gas Phase ◽  
Computational Study ◽  
Formation Enthalpy ◽  
Gold Atom ◽  
Orbital Energy ◽  
Knudsen Effusion ◽  
Energy Diagram ◽  
Unpaired Electrons ◽  
The Difference ◽  
Good Agreement

<p>In the present work, a computational study is performed in order to clarify the possible magnetic nature of gold. For such purpose, gas phase Au<sub>2</sub> (zero charge) is modelled, in order to calculate its gas phase formation enthalpy. The calculated values were compared with the experimental value obtained by means of Knudsen effusion mass spectrometric studies [5]. Based on the obtained formation enthalpy values for Au<sub>2</sub>, the compound with two unpaired electrons is the most probable one. The calculated ionization energy of modelled Au<sub>2</sub> with two unpaired electrons is 8.94 eV and with zero unpaired electrons, 11.42 eV. The difference (11.42-8.94 = 2.48 eV = 239.29 kJmol<sup>-1</sup>), is in very good agreement with the experimental value of 226.2 ± 0.5 kJmol<sup>-1</sup> to the Au-Au bond<sup>7</sup>. So, as expected, in the specie with none unpaired electrons, the two 6s<sup>1</sup> (one of each gold atom) are paired, forming a chemical bond with bond order 1. On the other hand, in Au<sub>2</sub> with two unpaired electrons, the s-d hybridization prevails, because the relativistic contributions. A molecular orbital energy diagram for gas phase Au<sub>2</sub> is proposed, explaining its paramagnetism (and, by extension, the paramagnetism of gold clusters and nanoparticles).</p>

Experimental and Computational Thermochemical Study and Solid-Phase Structure of 5,5-Dimethylbarbituric Acid

2010 ◽  
Vol 114 (10) ◽  
pp. 3583-3590 ◽  
Author(s):  
María Victoria Roux ◽  
Rafael Notario ◽  
Concepción Foces-Foces ◽  
Manuel Temprado ◽  
Francisco Ros ◽  
...  
Keyword(s):  
Phase Structure ◽  
Solid Phase ◽  
Thermochemical Study

scholarly journals Calculation of the Isobaric Heat Capacities of the Liquid and Solid Phase of Organic Compounds at 298.15K by Means of the Group-Additivity Method

Molecules ◽  
2020 ◽  
Vol 25 (5) ◽  
pp. 1147
Author(s):  
Rudolf Naef
Keyword(s):  
Experimental Data ◽  
Heat Capacity ◽  
Goodness Of Fit ◽  
Cross Validation ◽  
Solid Phase ◽  
Linear Equations ◽  
Heat Capacities ◽  
Molecular Volume ◽  
Complementary Method ◽  
Standard Deviations

The calculation of the isobaric heat capacities of the liquid and solid phase of molecules at 298.15 K is presented, applying a universal computer algorithm based on the atom-groups additivity method, using refined atom groups. The atom groups are defined as the molecules’ constituting atoms and their immediate neighbourhood. In addition, the hydroxy group of alcohols are further subdivided to take account of the different intermolecular interactions of primary, secondary, and tertiary alcohols. The evaluation of the groups’ contributions has been carried out by solving a matrix of simultaneous linear equations by means of the iterative Gauss–Seidel balancing calculus using experimental data from literature. Plausibility has been tested immediately after each fitting calculation using a 10-fold cross-validation procedure. For the heat capacity of liquids, the respective goodness of fit of the direct (r2) and the cross-validation calculations (q2) of 0.998 and 0.9975, and the respective standard deviations of 8.24 and 9.19 J/mol/K, together with a mean absolute percentage deviation (MAPD) of 2.66%, based on the experimental data of 1111 compounds, proves the excellent predictive applicability of the present method. The statistical values for the heat capacity of solids are only slightly inferior: for r2 and q2, the respective values are 0.9915 and 0.9874, the respective standard deviations are 12.21 and 14.23 J/mol/K, and the MAPD is 4.74%, based on 734 solids. The predicted heat capacities for a series of liquid and solid compounds have been directly compared to those received by a complementary method based on the "true" molecular volume and their deviations have been elucidated.

A mathematical model for the flotation of waste activated sludge

2002 ◽  
Vol 46 (11-12) ◽  
pp. 203-208
Author(s):  
K. Fujisaki ◽  
M. El-Zahar
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Gas Phase ◽  
Solid Phase ◽  
Growth Curves ◽  
Vertical Axis ◽  
Waste Activated Sludge ◽  
Flotation Process ◽  
Hindered Settling ◽  
Similar Character

A mathematical model that describes a batch flotation process is presented. The model employed a similar method to the hindered settling of flocculated material. This idea is based on our experimental results that the time growth curves of separated liquor zone showed a similar character to the settling curve of flocculated material, when the vertical axis reversed. In this model, it is also assumed that the gas phase and solid phase have the same movement, that is microbubbles and solid sludge particles joined to form aggregated floc. By comparing the numerical prediction with experimental data, the usefulness of the model is confirmed and some examples of flotation simulation are demonstrated.

Correlation between global thermodynamic functions and experimental data in multicomponent heterogeneous systems

2016 ◽  
Vol 94 (2) ◽  
pp. 113-119 ◽  
Author(s):  
Igor Povar ◽  
Oxana Spinu
Keyword(s):  
Experimental Data ◽  
Thermodynamic Functions ◽  
Solid Phase ◽  
Heterogeneous Systems ◽  
Thermodynamic Characteristics ◽  
Alkaline Solutions ◽  
Precipitation Process ◽  
Mutual Transformation ◽  
Homogeneous Solutions ◽  
Different Temperatures

The correlation between global thermodynamic functions and such experimental data, which quantitatively characterize the precipitation–dissolution processes of sparingly soluble compounds, as the degree of precipitation and residual concentrations of the solid-phase components in saturated solutions under real conditions, taking into account the complex formation reactions, has been deducted. The paper intends also to introduce widely formal thermodynamic methods for forecasting the conditions of mutual transformation of solid phases through chemical synthesis by precipitation methods, optimization of coprecipitation methods, fractional precipitation from homogeneous solutions, and separation and analysis of chemical compounds. Within the method of residual concentrations, the thermodynamic parameters of the process of precipitating cadmium ions with potassium decanoate from acid and alkaline solutions for different temperatures were investigated. On the basis of the experimentally determined degree of precipitation and its dependence on temperature, the temperature coefficients and overall thermodynamic characteristics of the precipitation process ([Formula: see text], [Formula: see text], and [Formula: see text]) were determined. The optimum conditions of the investigated process of precipitation have been established.

scholarly journals Charting Hydrogen Bond Anisotropy

2019 ◽  
Author(s):  
Diogo Santos-Martins ◽  
Stefano Forli
Keyword(s):  
Hydrogen Bond ◽  
Chemical Biology ◽  
Solid Phase ◽  
Electronic Configuration ◽  
Interaction Energies ◽  
X Ray ◽  
X Ray Crystallography ◽  
Chemical Groups ◽  
High Degree ◽  
Context Free

<div>Hydrogen bond (HB) is an essential interaction in countless phenomena, and regulates the chemistry of life. HBs are characterized by two main features, strength and directionality, with a high degree of heterogeneity across different chemical groups. These characteristics are dependent on the electronic configuration of the atoms involved in the interaction, which, in turn, is influenced strongly by the molecular environment where they are found. Studies based on the analysis of HB in solid phase, such as X-ray crystallography, suffer from significant biases due to the packing forces. These will tend to better describe strong HBs at the expenses of weak ones, which are either distorted or under represented. Using quantum mechanics (QM), we calculated interaction energies for about a hundred acceptor and donors, in a rigorously defined set of geometries. We performed about 180,000 independent QM calculations, covering all relevant angular components, and mapping strength and directionality in a context free from external biases, with both single-site and cooperative HBs. We show that by quantifying directionality, there is not correlation with strength, and therefore these two components need to be addressed separately. Results demonstrate that there are very strong HB acceptors (e.g.,DMSO) with nearly isotropic interactions, and weak ones (e.g.,thioacetone) with a sharp directional profile. Similarly, groups can have comparable directional propensity, but be very distant in the strength spectrum (e.g., thioacetone and pyridine). These findings have implications for biophysics and molecular recognition, providing new insight for chemical biology, protein engineering, and drug design. The results require rethinking the way directionality is described, with implications for the thermodynamics of HB.</div>

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