scholarly journals From Structure to Atoms: Compression/Tension Systems to a Molecular Tensegrity

Leonardo ◽  
2021 ◽  
pp. 1-11
Author(s):  
J. David Van Horn ◽  
Dayu Wang
Keyword(s):  
Subunit Structure ◽  
Particle Interactions ◽  
Covalent Bonds ◽  
Architectural Engineering ◽  
Macroscopic Structure ◽  
Ionic Bonds ◽  
Tension And Compression ◽  
Structural Analogy ◽  
Molecular Bonding ◽  
Tension Members

Abstract We reconsider macroscopic structure, including tensegrity structures, as ensembles of compression (C; repulsion) and tension (T; attraction) forces, and fit them to a triangular spectrum. Then, derivative structural analogy is made to the three classes of molecular bonding, as a bridge to microscopic structure. Basic molecular interactions and their “C/T” analogues are ionic bonds (with continuous compression/discontinuous tension), or metallic bonds (with both continuous tension and compression), or covalent bonds (with discontinuous compression/continuous tension—a tensegrity structure). The construction of tensegrity sculptures of particle interactions and the covalent molecules dihydrogen, methane, diborane, and benzene using tension and compression elements follows. We derived and utilized two properties in this analysis: 1) a “simplest tensegrity” subunit structure and 2) interpenetrating, discontinuous compressive members—tension members may also be discontinuous. This approach provides new artistic models for molecules and materials, and may inform future artistic, architectural, engineering and scientific endeavors.

First-Principles Study of Ag3Sn, AgZn3 and Ag5Zn8 Intermetallic Compounds

2021 ◽  
Vol 871 ◽  
pp. 254-263
Author(s):  
Zhan Cheng ◽  
Guan Xing Zhang ◽  
Wei Min Long ◽  
Svitlana Maksymova ◽  
Jian Xiu Liu
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Elastic Anisotropy ◽  
Constant Density ◽  
Mulliken Population ◽  
Covalent Bonds ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Anisotropy Index ◽  
Ionic Bonds

The first-principles calculations by CASTEP program based on the density functional theory is applied to calculate the cohesive energy, enthalpy of formation, elastic constant, density of states and Mulliken population of Ag3Sn、AgZn3 and Ag5Zn8. Furthermore, the elastic properties, bonding characteristics, and intrinsic connections of different phases are investigated. The results show that Ag3Sn、AgZn3 and Ag5Zn8 have stability structural, plasticity characteristics and different degrees of elastic anisotropy; Ag3Sn is the most stable structural, has the strongest alloying ability and the best plasticity. AgZn3 is the most unstable structure, has the worst plasticity; The strength of Ag5Zn8 is strongest, AgZn3 has the weakest strength, the largest shear resistance, and the highest hardness. Ag5Zn8 has the maximum Anisotropy index and Ag3Sn has the minimum Anisotropy index. Ag3Sn、AgZn3 and Ag5Zn8 are all have covalent bonds and ionic bonds, the ionic bonds decrease in the order Ag3Sn>Ag5Zn8>AgZn3 and covalent bonds decreases in the order Ag5Zn8>Ag3Sn>AgZn3.

The Influence of Nanostructured Metal Oxides and Unsaturated Acids on Peroxide Cross-Linking of Ethylene-Octene Rubber

2012 ◽  
Vol 714 ◽  
pp. 271-276 ◽  
Author(s):  
Martyna Pingot ◽  
Tomasz Pingot ◽  
Magdalena Maciejewska ◽  
Marian Zaborski
Keyword(s):  
Metal Oxides ◽  
Sem Images ◽  
Covalent Bonds ◽  
Dispersion Degree ◽  
Link Density ◽  
Ionic Bonds ◽  
Density Analysis ◽  
Elastomer Composites ◽  
Nanostructured Metal Oxides ◽  
Nanostructured Metal

This paper deals with blends of ethylene-octene rubber (POE) with nanostructured metal oxides: magnesium oxide (MgO), calcium oxide (CaO), zinc oxide (ZnO) and unsaturated acids: itaconic acid (IA), sorbic acid (SA) and crotonic acid (CA), as co-agents. Dicumyl peroxide (DCP) was used as a vulcanizing agent. Elastomer composites were prepared in Brabender measuring mixer N50. Rheometric properties of rubber mixes and crosslink density of vulcanizates were measured. Mechanical properties of the samples were also investigated. Dispersion degree of coagents in elastomer matrix was studied by SEM images. Cross-link density analysis revealed that POE vulcanizates contained both ionic bonds and covalent bonds. The results showed that the nanostructured metal oxides and unsaturated acids used as co-agents can greatly improve the modulus at 100% of elongation and tensile strength of the vulcanizates.

scholarly journals Enhancement of EPDM Crosslinked Elastic Properties by Association of Both Covalent and Ionic Networks

Polymers ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 3161
Author(s):  
Chloé Larrue ◽  
Véronique Bounor-Legaré ◽  
Philippe Cassagnau
Keyword(s):  
Metal Salts ◽  
Reversible Systems ◽  
Covalent Bonds ◽  
Long Period ◽  
Compression Set ◽  
Metallic Salts ◽  
Ionic Bonds ◽  
Physical And Chemical ◽  
Ethylene Propylene Diene Terpolymer ◽  
Physical Crosslinking

The objective of this study was to replace elastomer crosslinking based on chemical covalent bonds by reversible systems under processing. One way is based on ionic bonds creation, which allows a physical crosslinking while keeping the process reversibility. However, due to the weak elasticity recovery of such a physical network after a long period of compression, the combination of both physical and chemical networks was studied. In that frame, an ethylene-propylene-diene terpolymer grafted with maleic anhydride (EPDM-g-MA) was crosslinked with metal salts and/or dicumyl peroxide (DCP). Thus, the influence of these two types of crosslinking networks and their combination were studied in detail in terms of compression set. The second part of this work was focused on the influence of different metallic salts (KOH, ZnAc2) and the sensitivity to the water of the physical crosslinking network. Finally, the combination of ionic and covalent network allowed combining the processability and better mechanical properties in terms of recovery elasticity. KAc proved to be the best ionic candidate to avoid water degradation of the ionic network and then to preserve the elasticity recovery properties under aging.

scholarly journals First principle study of occupancy, bonding characteristics and alloying effect of Zr, Nb, V in bulk γ-Fe(C)

2020 ◽  
Vol 213 ◽  
pp. 01019
Author(s):  
Fei Liu ◽  
Shan Cong ◽  
Long Hao
Keyword(s):  
Solid Solution ◽  
Covalent Bond ◽  
Alloy Element ◽  
Chemical Bonds ◽  
Covalent Bonds ◽  
Binding Characteristics ◽  
Crystal Cell ◽  
Ionic Bonds ◽  
Crystal Cells ◽  
Bonding Characteristics

The total energy, binding characteristics, density of states, charge distribution and differential charge density of γ-Fe(C)-M crystal cells formed by solid solution of Zr, Nb and V in γ-Fe(C) were calculated by using the first-principles method. Thus, the mechanism of Zr, Nb, and V with γ-Fe(C) was investigated in this paper. The results show that Zr, Nb and V all preferentially replaced the Fe atoms which are at the top angle in γ-Fe(C). Crystal cell reaches its highest stability after V solid solution. Nb reaches after it, and Zr is relatively weak. In the γ-Fe(C)-Zr cell, Fe-Zr covalent bond and Zr-C ionic bond are the main chemical bonds. In the γ-Fe(C)-Nb and γ-Fe(C)-V cells, Fe-Nb and Fe-V covalent bonds are the main chemical bonds with a number of Nb-C and V-C ionic bonds. After solid solution, the electron cloud density around C atom changed little, while Fe atom changed obviously. The orbital electrons around Fe atoms in γFe(C)-V has maximal distribution, which means that the electrons delocalized most and most of the electrons are bonding. It is the main factor for the increase in the binding energy of crystal cell. The effects of Zr, Nb, V solution on austenitic stability are investigated by studying the influence of alloy element on γFe(C) electronic structure.

scholarly journals Demonstrating Bonds and Forces: From Nitrogen to Nanotubes

2013 ◽  
pp. 79-89
Keyword(s):  
Hydrogen Bonds ◽  
Covalent Bonds ◽  
Dipole Interactions ◽  
Ionic Bonds

In this exercise students will study chemical forces such as covalent bonds, ionic bonds, ion-dipole interactions and hydrogen bonds.

Calculation of the BO3 triangle to BO4 tetrahedron ratio in borates

2002 ◽  
Vol 217 (5) ◽  
Author(s):  
E. Parthé
Keyword(s):  
Crystal Structures ◽  
Composition Range ◽  
Chemical Formula ◽  
Covalent Bonds ◽  
Oh Groups ◽  
Proper Number ◽  
Anion Complex ◽  
Ionic Bonds ◽  
Complex Forms ◽  
Covalently Bound

AbstractA bonding model, valid for alimited group of borates, is formulated which allows the ratio of triangularly to tetrahedrally coordinated B atoms to be calculated from the chemical formula. The anion complex, which is formed by covalently bound atoms, has non-directed ionic bonds with the surrounding cations. To complete its electron octet, each O atoms of the complex forms exactly two covalent bonds either with 2 B and/or with 1 B and 1 H atom, depending on the number of OH groups. The B atoms have no preference for either triangular or tetrahedral O coordination. However, a change of a B-O base triangle to an isoelectronic base tetrahedron decreases the number of O atoms which can be used for B-O-H bonds and increases the number of shared O atoms engaged in B-O-B bonds - and vice versa. The ratio of B-O triangles to tetrahedra is adjusted such that O atoms can form the proper number of B-O-B and/or B-O-H bonds. Using the model one can also prove that a borate with OH groups and all its dehydration products (independent whether they are crystallized or a glass) should have the same ratio of three- to four-coordinated B atoms. Under the presupposition that the bonding model is applicable, one can specify a simple mixture of base triangles and/or base tetrahedra with which it should be possible to construct an anion complex. The observed complex is either built up with this simple mixture or with a mixture of base polyhedra derived from the simple one by cross-substitution which does not change the triangle to tetrahedron ratio. The realization of the bonding model is in principle possible only within a restricted composition range in which lie one quarter of the known borates. The equation to calculate the triangle to tetrahedron ratio has been tested on all borates within this range. An agreement was found for 85 percent of the 222 investigated crystal structures.

scholarly journals Towards a Density-Based Description of Chemical Bonds and Noncovalent Interactions with Pauli Energy

2022 ◽  
Author(s):  
Shubin Liu ◽  
Shujing Zhong ◽  
Xin He ◽  
Siyuan Liu ◽  
Bin Wang ◽  
...  
Keyword(s):  
Strong Interaction ◽  
Theoretical Foundation ◽  
Noncovalent Interactions ◽  
Van Der Waals Forces ◽  
Noncovalent Interaction ◽  
Chemical Bonds ◽  
Interaction Index ◽  
Covalent Bonds ◽  
Covalent Interaction ◽  
Ionic Bonds

Chemical bonds and noncovalent interactions are extraordinarily important concepts in chemistry and beyond. Using density-based quantities to describe them has a long history in the literature, yet none can satisfactorily describe the entire spectrum of interactions from strong chemical bonds to weak van der Waals forces. In this work, employing Pauli energy as the theoretical foundation, we fill in that knowledge gap. Our results show that the newly established density-based index can describe single and multiple covalent bonds, ionic bonds, metallic bonds, and different kinds of noncovalent interactions, all with unique and readily identifiable signature shapes. Two new descriptors, NBI (nonbonding and bonding identification) index and USI (ultra-strong interaction) index, have been introduced in this work. Together with NCI (noncovalent interaction) and SCI (strong covalent interaction) indexes already available in the literature, a density-based description of both chemical bonds and noncovalent interactions is accomplished.

GELATION MECHANISMS

2012 ◽  
Vol 26 (27) ◽  
pp. 1230019 ◽  
Author(s):  
ÖNDER PEKCAN ◽  
SELIM KARA
Keyword(s):  
Sol Gel ◽  
Theoretical Models ◽  
Polymer Chains ◽  
Gel Point ◽  
Covalent Bonds ◽  
Polymeric Systems ◽  
Composite Gels ◽  
Theoretical Predictions ◽  
Ionic Bonds ◽  
Gel Phase

In this paper, we survey the gelation mechanisms for various polymeric systems which are classified by the type and the strength of the cross-linkages. These are the "irreversible" gels that are cross-linked chemically by covalent bonds and the "reversible" gels that are cross-linked physically by hydrogen or ionic bonds and by the physical entanglement of polymer chains. Some of the natural polymer gels fall into the class of physical gels, among which the red algae that has attracted attention for various applications is discussed in detail. Various composite gels, formed from mixture of physical and chemical gels are also discussed in the last section of the article. Theoretical models describe the gelation as a process of random linking of subunits to larger and larger molecules by formation of an infinite network, where no matter what type of objects are linked, there is always a critical "gel point" at which the system behaves neither as a liquid nor as a solid on any length scale. The Flory–Stockmayer theory and percolation theory provide bases for modeling this sol–gel phase transition. The experimental techniques for measuring the critical exponents for sol–gel phase transitions in different polymeric systems are introduced and the validation of various theoretical predictions are surveyed.

Subunit Structure of Human Factor VIII

1975 ◽  
Author(s):  
J. A. van Mourik ◽  
W. T. LaBruyère ◽  
I. A. Mochtar
Keyword(s):  
Molecular Weight ◽  
Ionic Strength ◽  
Factor Viii ◽  
Apparent Molecular Weight ◽  
Subunit Structure ◽  
Single Chain ◽  
Covalent Bonds ◽  
Single Polypeptide Chain ◽  
Human Factor Viii ◽  
Low Ionic Strength

Several investigations have shown that factor VIII is a high molecular weight aggregate and that both non-covalent and disulphide bonds contribute to the stabilization of the macromolecular factor VIII aggregate. As shown previously (1) disruption of non-covalent bonds can be accomplished at relatively low ionic strength and neutral pH and results via a series of homologous oligomers (having constant charge/mass ratios) in 2 immunologically non-related subunits. Thus, the generally accepted concept that factor VIII is constructed of identical subunits seems incorrect. For several reasons we assume that the observed fragmentation at low ionic strength is not due to proteolytic breakdown. However, this view is not favoured by the observation that tryptic and plasmic digestion of factor VIII (in aggregated form) results in gel electrophoresis patterns comparable with those obtained of factor VIII after low ionic strength dissociation. Further, evidence will be presented that the assumption that reduction of factor VIII under denaturating conditions results in a single polypeptide chain is also no longer tenable. As far as the reduction of aggregated factor VIII is concerned our observations agree with data from the literature, that is, reduction of factor VIII results in 1 major subunit with an apparent molecular weight of approximately 270.000. However, when factor VIII is first dissociated at low ionic strength followed by reduction, smaller fragments appear in the electrophoresis pattern. Thus, it seems most likely that the apparent single chain subunit is in fact, constructed of smaller non-covalently linked fragments.(1) J. A. van Mourik et al. Thrombosis Research, 4, 155, 1974.

scholarly journals Investigations on the general properties of biomass-based aldehyde tanned sheep fur for its selective post-tanning processing

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Wei Ding ◽  
Ya-nan Wang ◽  
Jianfei Zhou ◽  
Haiteng Liu ◽  
Xiaoyan Pang ◽  
...  
Keyword(s):  
Schiff Base ◽  
Collagen Fiber ◽  
Processing Conditions ◽  
Covalent Bonds ◽  
Acid Sensitivity ◽  
General Properties ◽  
Dyeing Process ◽  
Chrome Tanning ◽  
Ionic Bonds ◽  
Base Structure

Abstract Dialdehyde sodium alginate (DSA) is an alternative chrome-free tanning material for fur production. To obtain satisfactory resultant fur and provide suggestions for the usage of DSA in fur making, the general properties of DSA tanned sheep fur were systematically investigated. The tanning mechanism of DSA was analyzed and it was verified that DSA was mainly combined with collagen fiber by forming Schiff base covalent bonds while supplemented by a small number of hydrogen bonds and ionic bonds. Due to the acid sensitivity of Schiff base structure, DSA tanned fur had poor resistance to acid rinsing but had excellent resistance to washing and good fatliquoring performance. Also, it had good resistances to yellowing and reductant. After being retanned by chrome tanning agent, the fur was capable of enduring a high-temperature dyeing process (68 °C for 8 h). Overall, DSA tanned sheep fur had favorable properties under appropriate post-tanning processing conditions to manufacture light-colored or dark-colored fur products with desirable physical properties. Graphical abstract

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