Theoretical prediction of physical parameters of GexSb20−x Te80 (x = 11, 13, 15, 17, 19) bulk glassy alloys

2014 ◽  
Vol 32 (4) ◽  
pp. 661-668 ◽  
Author(s):  
Ishu Sharma ◽  
Monisha Maheshwari
Keyword(s):  
Coordination Number ◽  
Bond Energy ◽  
Cohesive Energy ◽  
Lone Pair ◽  
Average Coordination Number ◽  
Physical Parameters ◽  
Calculated Density ◽  
Glassy Alloys ◽  
Mean Bond Energy ◽  
Lone Pair Electrons

AbstractPhysical properties of GexSb20−x Te80 (x = 11, 13, 15, 17, 19) bulk glassy alloys are examined theoretically. Lone pair electrons are calculated using an average coordination number (〈r〉) and the number of valence electrons, and are found to decrease with an addition of Ge. Mean bond energy (〈E〉) is proportional to glass transition temperature (Tg) and shows maxima near the chemical threshold. Cohesive energy of the system is calculated using chemical bond approach. A linear relation is found between cohesive energy, band gap (calculated theoretically and confirmed experimentally) and average heat of atomization. All these parameters are increasing with an increase in Ge content. A relation between average single bond energy and photon energy is discussed. Compactness of the structure is measured from the calculated density of the glass. An attempt is made to discuss the results in terms of structure of the glass or equivalently with average coordination number.

A Study of the Physical Properties of Te15(Se100-xBix)85 Glassy Alloys

2010 ◽  
Vol 305-306 ◽  
pp. 61-69 ◽  
Author(s):  
Kameshwar Kumar ◽  
Nagesh Thakur ◽  
S.C. Katyal ◽  
Pankaj Sharma
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Coordination Number ◽  
Bond Energy ◽  
Cohesive Energy ◽  
Energy Gap ◽  
Average Coordination Number ◽  
Glassy Alloys ◽  
Mean Bond Energy

In the present communication, a study was made of the compositional variation of physical properties: average coordination number (<r>), average number of constraints (Ncon), number of lone-pair electrons (L), mean bond energy (<E>), cohesive energy (CE), average heat of atomization (Hs), glass transition temperature (Tg), density (ρ) and theoretical energy gap (Eg) for Te15(Se100-xBix)85 (x = 0, 1, 2, 3, 4, 5at%) glassy alloys. The mean bond energy and the cohesive energy have been calculated using the chemical bond approach (CBA). The glass transition temperature was calculated using the Tichy-Ticha approach, and has been found to increase with Bi content. The mean bond energy is found to be proportional to the glass transition temperature and the average coordination number. It has been found that the average coordination number, average number of constraints, mean bond energy and density increase, whereas the cohesive energy, average heat of atomization and theoretical energy gap decrease with increasing Bi content in Se-Te alloys.

scholarly journals Analysis of glass forming ability using percolation concept and tunability of physical parameters of a-Ge12Se76 - xAs12Bix glassy semiconductors

2018 ◽  
Vol 36 (2) ◽  
pp. 242-254 ◽  
Author(s):  
Ishu Sharma ◽  
Sruthi Sunder
Keyword(s):  
Cohesive Energy ◽  
Lone Pair ◽  
Glass Forming Ability ◽  
Glassy Matrix ◽  
Physical Parameters ◽  
Volume Percentage ◽  
Glass Forming ◽  
Mean Bond Energy ◽  
Density Values ◽  
Lone Pair Electrons

AbstractGlass forming ability of lone-pair semiconductors was analyzed for (x = 0, 2, 4, 6, 8, 10) system. Values of lone pair electrons L were calculated using average coordination number of valence electrons. These values were found to decrease, as the system was moving towards the rigid region. L > 3 values showed vitreous state. Deviation of the stoichiometry confirmed the chalcogen-rich region. A linear correlation was found between the mean bond energy and glass transition temperature. Chemical Bond Approach model was applied to calculate the cohesive energy of the system. A linear relationship was found to exist between the cohesive energy and the theoretical band gap, calculated using Shimakawa relation. A decrease in both parameters was explained on the basis of average stabilization energy and electronegativity of the system. The density values were found to increase and may account for higher refractive index of the system. Large Bohr radius of the Bi atom accounted for an increase in the polarizability. Other parameters viz. degree of covalency, packing density, compactness, molar volume, free volume percentage, excess volume and polaron radius were also calculated. An effort was made to correlate the effect of Bi addition to Ge12Se76-xAs12Bixlone-pair semiconductor on the basis of the structure of the glassy matrix or the connectedness of the material.

scholarly journals The effect of adding CsCl content on physicochemical properties of (GeS2–Sb2S3)100-x(CsCl)x (0 ≤ x ≤ 40 mol%) chalcohalide glasses

2021 ◽  
Author(s):  
Imed Boukhris ◽  
Imen Kebaili
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Bond Energy ◽  
Unit Volume ◽  
Chemical Properties ◽  
Lone Pair ◽  
Physico Chemical ◽  
Chalcohalide Glasses ◽  
Mean Bond Energy ◽  
Lone Pair Electrons

Abstract The physico-chemical properties of (GeS2–Sb2S3)100-x(CsCl)x (0 ≤ x ≤ 40 mol%) chalcohalide glasses were theoretically studied. The band gap (Eg) of the studied glass system was estimated and was found to increase by adding the CsCl content. Furthermore, the positions of the valence band and conduction band edges was determined. The results reveal that the molar volume (Vm) of the studied samples increased while the density (ρ) and the number of atoms per unit volume (N) decreased with increasing the CsCl content. The overall coordination number (CN), constraints number (Ns) and overall mean bond energy (<E>) were computed using the chemical bond approach and were found to decrease. In contrast, the number of lone-pair electrons (LP) and cohesive energy (CE) increased. Finally, the glass-transition temperature (Tg) was also estimated based on the overall mean bond energy, and was found to decrease with increasing the CsCl content.

scholarly journals Effect of Sn Incorporation on Physical Parameters of Sb-Se Glassy System

2020 ◽  
Vol 12 (4) ◽  
pp. 545-554
Author(s):  
R. Khajuria ◽  
A. Sharma ◽  
P. Sharma
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Band Gap ◽  
Bond Energy ◽  
Chalcogenide Glasses ◽  
Lone Pair ◽  
Physical Parameters ◽  
Glassy System ◽  
Almost All

The rationale of this study is to investigate band gap tailoring of Sb-Se-Sn chalcogenide glasses. This study has been accompanied by the assessment of various theoretical parameters such as average co-ordination number, Lone-pair of electrons, number of constraints, average heat of atomization, mean bond energy and glass transition temperature. It has been observed that almost all these physical parameters have been enhanced with the increase in tin (Sn) content except Lone-pair of electrons. The number of lone-pair electrons has been decreased with the increase in Sn content. The glass transition temperature has been observed to increase due to the addition of Sn atom in the Se-Sb glassy system. The band gap is decreasing with increase in Sn content due to overall decrease in the average single bond energy of the Sb-Se-Sn glassy system.  

scholarly journals Bond-length distributions for ions bonded to oxygen: metalloids and post-transition metals

2018 ◽  
Vol 74 (1) ◽  
pp. 63-78 ◽  
Author(s):  
Olivier Charles Gagné ◽  
Frank Christopher Hawthorne
Keyword(s):  
Transition Metal ◽  
Metal Ions ◽  
Bond Length ◽  
Coordination Number ◽  
Lone Pair ◽  
Transition Metal Ions ◽  
Length Variation ◽  
Coordination Polyhedra ◽  
Bond Lengths ◽  
Lone Pair Electrons

Bond-length distributions have been examined for 33 configurations of the metalloid ions and 56 configurations of the post-transition metal ions bonded to oxygen, for 5279 coordination polyhedra and 21 761 bond distances for the metalloid ions, and 1821 coordination polyhedra and 10 723 bond distances for the post-transition metal ions. For the metalloid and post-transition elements with lone-pair electrons, the more common oxidation state between n versus n+2 is n for Sn, Te, Tl, Pb and Bi and n+2 for As and Sb. There is no correlation between bond-valence sum and coordination number for cations with stereoactive lone-pair electrons when including secondary bonds, and both intermediate states of lone-pair stereoactivity and inert lone pairs may occur for any coordination number > [4]. Variations in mean bond length are ∼0.06–0.09 Å for strongly bonded oxyanions of metalloid and post-transition metal ions, and ∼0.1–0.3 Å for ions showing lone-pair stereoactivity. Bond-length distortion is confirmed to be a leading cause of variation in mean bond lengths for ions with stereoactive lone-pair electrons. For strongly bonded cations (i.e. oxyanions), the causes of mean bond-length variation are unclear; the most plausible cause of mean bond-length variation for these ions is the effect of structure type, i.e. stress resulting from the inability of a structure to adopt its characteristic a priori bond lengths.

Modeling the cohesive energy and melting point of nanoparticles by their average coordination number

2008 ◽  
Vol 145 (9-10) ◽  
pp. 432-437 ◽  
Author(s):  
M. Attarian Shandiz ◽  
A. Safaei ◽  
S. Sanjabi ◽  
Z.H. Barber
Keyword(s):  
Melting Point ◽  
Coordination Number ◽  
Cohesive Energy ◽  
Average Coordination Number

Effect of Bi Additions upon the Physical Properties of Germanium Telluride Glassy Semiconductors

2009 ◽  
Vol 293 ◽  
pp. 107-112 ◽  
Author(s):  
Ambika Sharma ◽  
P.B. Barman
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Physical Properties ◽  
Molar Volume ◽  
Glassy Alloy ◽  
Lone Pair ◽  
Germanium Telluride ◽  
Glassy Alloys ◽  
Lone Pair Electrons

The effect of bismuth (Bi) additions upon the physical properties, coordination number (m), constraints (Nc), density (ρ), molar volume (Vm), cohesive energy (CE), lone pair electrons (L) and glass transition temperature (Tg) of Ge20Te80-xBix (x = 0, 1.5, 2.5, 5.0) bulk glassy alloy has been investigated. The density and molar volume of the glassy alloys has been found to increase with increasing Bi content. The CE of the investigated samples has been calculated by using the chemical bond approach (CBA) and is correlated with a decrease in the optical band-gap with increasing Bi content. The glass transition temperature has been estimated by using the Tichy–Ticha approach and was found to increase with an increase in the Bi content.

Effect of delocalization of nonbonding electron density on the stability of the M–Ccarbene bond in main group metal-imidazol-2-ylidene complexes: a computational and structural database study

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Samuel Tetteh ◽  
Albert Ofori
Keyword(s):  
Electron Density ◽  
Lone Pair ◽  
Main Group ◽  
Binding Energies ◽  
Electrostatic Model ◽  
Group Metal ◽  
Main Group Metal ◽  
Structural Database ◽  
The Stability ◽  
Lone Pair Electrons

Abstract The M–Ccarbene bond in metal (M) complexes involving the imidazol-2-ylidene (Im) ligand has largely been described using the σ-donor only model with donation of σ electrons from the sp-hybridized orbital of the carbene carbon into vacant orbitals on the metal centre. Analyses of the M–Ccarbene bond in a series of group IA, IIA and IIIA main group metal complexes show that the M-Im interactions are mostly electrostatic with the M–Ccarbene bond distances greater than the sum of the respective covalent radii. Estimation of the binding energies of a series of metal hydride/fluoride/chloride imidazol-2-ylidene complexes revealed that the stability of the M–Ccarbene bond in these complexes is not always commensurate with the σ-only electrostatic model. Further natural bond orbital (NBO) analyses at the DFT/B3LYP level of theory revealed substantial covalency in the M–Ccarbene bond with minor delocalization of electron density from the lone pair electrons on the halide ligands into antibonding molecular orbitals on the Im ligand. Calculation of the thermodynamic stability of the M–Ccarbene bond showed that these interactions are mostly endothermic in the gas phase with reduced entropies giving an overall ΔG > 0.

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