scholarly journals Lattice dynamics of III–V compounds

1969 ◽  
Vol 47 (4) ◽  
pp. 451-462 ◽  
Author(s):  
R. Banerjee ◽  
Y. P. Varshni
Keyword(s):  
Experimental Data ◽  
Force Constant ◽  
Frequency Distribution ◽  
Effective Charge ◽  
Lattice Dynamics ◽  
Distribution Functions ◽  
Constant Field ◽  
X Ray ◽  
Debye Temperatures ◽  
General Force

The lattice dynamics of III–V compounds has been investigated on a 'rigid ion' type of model. The interactions are assumed to consist of Coulomb forces with an effective charge and a general force constant field up to and including second neighbors. Results are presented for the dispersion curves, frequency distribution functions, and effective calorimetric and X-ray Debye temperatures for AlSb, GaP, GaAs, and InSb. The agreement with the experimental data, where available, is reasonable.

Structure of 1,6-anhydro-β-D-glucopyranose in plastic crystal, orientational glass, liquid and ordinary glass forms: molecular modeling and X-ray diffraction studies

2021 ◽  
Vol 77 (1) ◽  
pp. 138-149
Author(s):  
Karolina Jurkiewicz ◽  
Wojciech Glajcar ◽  
Kamil Kamiński ◽  
László Temleitner ◽  
Andrzej Burian
Keyword(s):  
Experimental Data ◽  
Molecular Modeling ◽  
Distribution Functions ◽  
Face Centered Cubic ◽  
Plastic Crystal ◽  
X Ray Diffraction ◽  
Static Structure ◽  
X Ray ◽  
Orientational Glass ◽  
Molecular Arrangement

The structures of the plastic crystal (PC), orientational glass (OTG), liquid (LQ) and ordinary glass (OG) phases of 1,6-anhydro-β-D-glucopyranose (levoglucosan) have been investigated using X-ray diffraction and molecular modeling. The experimental diffraction data in the forms of static structure factors and pair distribution functions are analyzed in reciprocal and real spaces and compared with results of model-based simulations. A new approach to modeling the structure of the disordered phases, taking into account the intermolecular scattering contribution in the form of sharp Bragg peaks, the slowly varying intensity associated with intramolecular correlations and the diffusive component resulting from structural disorder, is applied. In the case of the LQ and OG samples, reverse Monte Carlo simulations are also used. The PC and OTG phases show long-range ordering of the hexagonal close-packed (hcp)-type structure up to 120 Å with random orientation of the molecules. Assuming a rigid molecular skeleton, isotropic free rotations of the molecules about their geometrical center in full and limited angular ranges are generated in theoretical models of the structure. It is demonstrated that the adoption of free rotations of the molecules leads to the best fits to experimental data for each studied phase of levoglucosan. The diffraction patterns of the LQ and OG samples show a relatively sharp first peak originating from quasi-Bragg planes of the densely packed face-centered cubic (fcc) type molecular arrangement. Moreover, the slowly varied intensity component of LQ and OG is practically the same as that of PC and OTG, suggesting that the intramolecular structure of these four phases does not change. Interestingly, structural correlations for the disordered LQ and OG states extend surprisingly far, up to about 50 Å. In addition, for all levoglucosan phases investigated, the paracrystalline disorder imposed on the generated models resulted in better compliance with the experimental data.

A Born–von Karman Force Constant Model for Aluminum

1974 ◽  
Vol 52 (17) ◽  
pp. 1714-1715 ◽  
Author(s):  
E. R. Cowley
Keyword(s):  
Experimental Data ◽  
Distribution Function ◽  
Force Constant ◽  
Frequency Distribution ◽  
Brillouin Zone ◽  
Normal Modes ◽  
Frequency Distribution Function ◽  
Von Karman ◽  
Von Kármán ◽  
Good Agreement

A Born–von Karman force constant model of aluminum, fitted to the frequencies of normal modes with wave vectors distributed throughout the Brillouin zone, is described, and the frequency distribution function calculated. The result is in very good agreement with a distribution function calculated directly from the experimental data.

scholarly journals Testing the Reverse Monte Carlo Method Using Scattering Data from Amorphous Ni2Zr

1992 ◽  
Vol 47 (5) ◽  
pp. 685-688
Author(s):  
M. Bionducci ◽  
F. Buffa ◽  
G. Licheri ◽  
G. Navarra
Keyword(s):  
Experimental Data ◽  
Monte Carlo ◽  
Distribution Functions ◽  
Scattering Data ◽  
Anomalous Scattering ◽  
Reverse Monte Carlo ◽  
X Ray ◽  
Reverse Monte Carlo Simulation ◽  
Partial Distribution ◽  
Reverse Monte Carlo Method

Abstract The reverse Monte Carlo simulation has been tested by modelling the partial distribution functions of amorphous Ni2Zr. Three runs of simulation involving experimental data from isotopic substitutions neutron scattering and X-ray anomalous scattering are presented

Influence of the static electron gas screening function on the lattice dynamics of sodium

1970 ◽  
Vol 48 (2) ◽  
pp. 183-192 ◽  
Author(s):  
D. J. W. Geldart ◽  
Roger Taylor ◽  
Y. P. Varshni
Keyword(s):  
Distribution Function ◽  
Lattice Dynamics ◽  
Phonon Frequency ◽  
Phonon Dispersion ◽  
Electron Gas ◽  
Phonon Dispersion Curves ◽  
X Ray ◽  
Debye Temperatures ◽  
Static Electron ◽  
Good Agreement

The static electron gas screening function calculated by Geldart and Taylor has been used in conjunction with the theory of Vosko, Taylor, and Keech to calculate the phonon dispersion curves, the effective calorimetric and X-ray Debye temperatures, and moments of the phonon frequency distribution function of sodium. The results which compare very favorably with those obtained using other screening functions give good agreement with experiment, indicating that the new screening function is reasonably adequate for calculations in sodium.

Evidence for ordered Fe3Ni

1987 ◽  
Vol 45 ◽  
pp. 216-217
Author(s):  
K.B. Reuter ◽  
D.B. Williams ◽  
J.I. Goldstein
Keyword(s):  
Experimental Data ◽  
Martensitic Transformation ◽  
Electron Diffraction ◽  
Room Temperature ◽  
Direct Evidence ◽  
Transformation Product ◽  
Iron Meteorites ◽  
X Ray ◽  
Ni Content ◽  
Temperature Transformation

In the Fe-Ni system, although ordered FeNi and ordered Ni3Fe are experimentally well established, direct evidence for ordered Fe3Ni is unconvincing. Little experimental data for Fe3Ni exists because diffusion is sluggish at temperatures below 400°C and because alloys containing less than 29 wt% Ni undergo a martensitic transformation at room temperature. Fe-Ni phases in iron meteorites were examined in this study because iron meteorites have cooled at slow rates of about 10°C/106 years, allowing phase transformations below 400°C to occur. One low temperature transformation product, called clear taenite 2 (CT2), was of particular interest because it contains less than 30 wtZ Ni and is not martensitic. Because CT2 is only a few microns in size, the structure and Ni content were determined through electron diffraction and x-ray microanalysis. A Philips EM400T operated at 120 kV, equipped with a Tracor Northern 2000 multichannel analyzer, was used.

scholarly journals Zeolite NaP1 Functionalization for the Sorption of Metal Complexes with Biodegradable N-(1,2-dicarboxyethyl)-D,L-aspartic Acid

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2518
Author(s):  
Dorota Kołodyńska ◽  
Yongming Ju ◽  
Małgorzata Franus ◽  
Wojciech Franus
Keyword(s):  
Experimental Data ◽  
Aspartic Acid ◽  
Ph Value ◽  
Complexing Agents ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
Modified Zeolite ◽  
X Ray ◽  
Slow Release Fertilizers ◽  
Pseudo Second Order

The possibility of application of chitosan-modified zeolite as sorbent for Cu(II), Zn(II), Mn(II), and Fe(III) ions and their mixtures in the presence of N-(1,2-dicarboxyethyl)-D,L-aspartic acid, IDHA) under different experimental conditions were investigated. Chitosan-modified zeolite belongs to the group of biodegradable complexing agents used in fertilizer production. NaP1CS as a carrier forms a barrier to the spontaneous release of the fertilizer into soil. The obtained materials were characterized by Fourier transform infrared spectroscopy (FTIR); surface area determination (ASAP); scanning electron microscopy (SEM-EDS); X-ray fluorescence (XRF); X-ray diffraction (XRD); and carbon, hydrogen, and nitrogen (CHN), as well as thermogravimetric (TGA) methods. The concentrations of Cu(II), Zn(II), Mn(II), and Fe(III) complexes with IDHA varied from 5–20 mg/dm3 for Cu(II), 10–40 mg/dm3 for Fe(III), 20–80 mg/dm3 for Mn(II), and 10–40 mg/dm3 for Zn(II), respectively; pH value (3–6), time (1–120 min), and temperature (293–333 K) on the sorption efficiency were tested. The Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin adsorption models were applied to describe experimental data. The pH 5 proved to be appropriate for adsorption. The pseudo-second order and Langmuir models were consistent with the experimental data. The thermodynamic parameters indicate that adsorption is spontaneous and endothermic. The highest desorption percentage was achieved using the HCl solution, therefore, proving that method can be used to design slow-release fertilizers.

scholarly journals Phase Relations in the ZrO2-MgO-FeOx System: Experimental Data and Assessment of Thermodynamic Parameters

2021 ◽  
Author(s):  
Ivan Saenko ◽  
O. Fabrichnaya
Keyword(s):  
Electron Microscopy ◽  
Experimental Data ◽  
Solid Solution ◽  
Thermodynamic Parameters ◽  
Spinel Phase ◽  
Experimental Investigations ◽  
X Ray ◽  
Heat Treated ◽  
Preliminary Phase ◽  
Scanning Electron

AbstractThermodynamic parameters were assessed for the MgO–FeOx system and combined with already available descriptions of ZrO2-FeOx and ZrO2-MgO systems to calculate preliminary phase diagrams for planning experimental investigations. Samples of selected compositions were heat treated at 1523, 1673 and 1873 K and characterized using x-ray and scanning electron microscopy combined with energy dispersive x-ray spectroscopy (SEM/EDX). Experiments indicated extension of cubic ZrO2 solid solution into the ternary system at 1873 K (75 mol.% ZrO2, 10 mol.% FeOx and 15 mol.% MgO) and limited solubility of 4 mol.% ZrO2 in spinel phase. Based on the obtained results thermodynamic parameters of C-ZrO2 and spinel phase were optimized.

scholarly journals Enhancing removal efficiency of anionic dye (Cibacron blue) using waste potato peels powder

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kahina Bouhadjra ◽  
Wahiba Lemlikchi ◽  
Azedine Ferhati ◽  
Samuel Mignard
Keyword(s):  
Experimental Data ◽  
Contact Time ◽  
Potato Peel ◽  
X Ray ◽  
Cibacron Blue ◽  
Anionic Dye ◽  
Experimental Parameters ◽  
Optimum Ph ◽  
Potato Peels ◽  
Scanning Electron

AbstractIn the present study, the potato peel waste (PP) was used for the removal of the anionic dye Cibacron Blue P3R from an aqueous solution, activated with phosphoric acid (PPa) and calcined at 800 °C (PPc). The materials were characterized by Scanning Electron Microscope, Energy dispersive X-ray analysis and Fourier Transform Infrared Spectroscopy. The effects of various experimental parameters (pH, dye concentration, contact time) were also studied. The experimental results have shown that PPc has a greater capacity compared to pp and ppa. The capacity of PP bio-char (PPc) is 270.3 mg g−1 compared to PP (100 mg g−1) and PPa (125 mg g−1). Equilibrium experiments at 180 min for all materials were carried out at optimum pH (2.2): 76.41, 88.6 and 94% for PP, PPa and PPc respectively; and the Langmuir models agreed very well with experimental data. The ability of sorbent for the sorption of CB dye follows this order: calcined > activated > native materials. Potato peel biochar (PPc) can be considered a promising adsorbent for removing persistent dyes from water.

scholarly journals Development and Evaluation of a Fluctuating Plume Model for Odor Impact Assessment

2021 ◽  
Vol 11 (8) ◽  
pp. 3310
Author(s):  
Marzio Invernizzi ◽  
Federica Capra ◽  
Roberto Sozzi ◽  
Laura Capelli ◽  
Selena Sironi
Keyword(s):  
Experimental Data ◽  
Distribution Functions ◽  
Plume Model ◽  
Probability Distribution Functions ◽  
Weibull Pdf ◽  
Fluctuating Plume ◽  
Concentration Statistics ◽  
Modified Weibull ◽  
Instantaneous Concentration ◽  
Mean Concentration

For environmental odor nuisance, it is extremely important to identify the instantaneous concentration statistics. In this work, a Fluctuating Plume Model for different statistical moments is proposed. It provides data in terms of mean concentrations, variance, and intensity of concentration. The 90th percentile peak-to-mean factor, R90, was tested here by comparing it with the experimental results (Uttenweiler field experiment), considering different Probability Distribution Functions (PDFs): Gamma and the Modified Weibull. Seventy-two percent of the simulated mean concentration values fell within a factor 2 compared to the experimental ones: the model was judged acceptable. Both the modelled results for standard deviation, σC, and concentration intensity, Ic, overestimate the experimental data. This evidence can be due to the non-ideality of the measurement system. The propagation of those errors to the estimation of R90 is complex, but the ranges covered are quite repeatable: the obtained values are 1–3 for the Gamma, 1.5–4 for Modified Weibull PDF, and experimental ones from 1.4 to 3.6.

scholarly journals Unbinding of Hyaluronan Accelerates the Enzymatic Activity of Bee Hyaluronidase

2011 ◽  
Vol 286 (41) ◽  
pp. 35699-35707 ◽  
Author(s):  
Attila Iliás ◽  
Károly Liliom ◽  
Brigitte Greiderer-Kleinlercher ◽  
Stephan Reitinger ◽  
Günter Lepperdinger
Keyword(s):  
Experimental Data ◽  
Quartz Crystal ◽  
Surface Loop ◽  
X Ray ◽  
Site Model ◽  
Substrate Interaction ◽  
Close Proximity ◽  
Binding Groove ◽  
The One ◽  
Best Fit

Hyaluronan (HA), a polymeric glycosaminoglycan ubiquitously present in higher animals, is hydrolyzed by hyaluronidases (HAases). Here, we used bee HAase as a model enzyme to study the HA-HAase interaction. Located in close proximity to the active center, a bulky surface loop, which appears to obstruct one end of the substrate binding groove, was found to be functionally involved in HA turnover. To better understand kinetic changes in substrate interaction, binding of high molecular weight HA to catalytically inactive HAase was monitored by means of quartz crystal microbalance technology. Replacement of the delimiting loop by a tetrapeptide interconnection increased the affinity for HA up to 100-fold, with a KD below 1 nm being the highest affinity among HA-binding proteins surveyed so far. The experimental data of HA-HAase interaction were further validated showing best fit to the theoretically proposed sequential two-site model. Besides the one, which had been shown previously in course of x-ray structure determination, a previously unrecognized binding site works in conjunction with an unbinding loop that facilitates liberation of hydrolyzed HA.

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