The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Maija Aksela - One of the best experts on this subject based on the ideXlab platform.
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the challenges of learning and teaching Chemical Bonding at different school levels using electrostatic interactions instead of the octet rule as a teaching model
Chemistry Education Research and Practice, 2018Co-Authors: Jarkko Joki, Maija AkselaAbstract:Teaching Chemical Bonding using the octet rule as an explanatory principle is problematic in many ways. The aim of this case study is to understand the learning and teaching of Chemical Bonding using a research-informed teaching model in which Chemical Bonding is introduced as an electrostatic phenomenon. The study posed two main questions: (i) how does a student's understanding of Chemical Bonding evolve from lower- to upper-secondary school when an electrostatic model of Chemical Bonding was used at the lower-secondary level? (ii) How does the teaching of octets/full shells at the upper-secondary level affect students’ understanding? The same students were interviewed after lower-secondary school and again during their first year at upper-secondary school. Their upper-level chemistry teachers were also interviewed. The interview data were analysed using the grounded theory method. The findings showed that the students’ earlier proper understanding of the electrostatic-interactions model at the lower-secondary level did not prevent the later development of less-canonical thinking. Teachers’ pedagogical content knowledge (PCK) of the explanatory principles of Chemical Bonding and how to use explanations in science education needs to be promoted in both pre-service teacher education and during in-service training.
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coulombic interaction in finnish middle school chemistry a systemic perspective on students conceptual structure of Chemical Bonding
Chemistry Education Research and Practice, 2015Co-Authors: Jarkko Joki, Jari Lavonen, Kalle Juuti, Maija AkselaAbstract:The aim of this study was to design a novel and holistic way to teach Chemical Bonding at the middle school level according to research on the teaching and learning of Bonding. A further aim was to investigate high achieving middle school students' conceptual structures concerning Chemical Bonding by using a systemic perspective. Students in one metropolitan area middle school were introduced to this newly designed model and their conceptual structures were studied by a clinical interview (n = 8) at the time when the students were concluding their studies at the middle school. The interview data were analysed by employing a systemic perspective on conceptual structures. Elements of conceptual structures such as concepts, simple models (mnemonic devices), explaining schemas, attributes and hypothesis constructs were identified and coded. Connections between the knowledge elements were also identified. An understanding of these connections helps to illuminate which components are necessary to build an adequate conceptual structure. The study revealed that applying principles relating to Coulombic interaction to understand Chemical Bonding requires the simultaneous appreciation of several factors: First, electron shells have to be understood in terms of energy levels. Second, the distance between the outer electrons and the nucleus has to be understood on the basis of electron shell construction. On the other hand, the effective nuclear charge also needs to be taken into account. The study introduces two new points of view to chemistry education research (CER): (1) a teaching model of Chemical Bonding that emphasises electric interaction as the background of most Bonding types was developed in the study. This responds to the identified need in CER to test alternative teaching models that avoid the octet framework. (2) In the field of chemistry education research, a systemic approach has not previously been widely used for the examination of conceptual structures. In addition, the systemic perception of the network structure, which consists of these constructions, helps to explain in more detail the relationship between the separate concepts and the constructions and their significance as a whole.
Jarkko Joki - One of the best experts on this subject based on the ideXlab platform.
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the challenges of learning and teaching Chemical Bonding at different school levels using electrostatic interactions instead of the octet rule as a teaching model
Chemistry Education Research and Practice, 2018Co-Authors: Jarkko Joki, Maija AkselaAbstract:Teaching Chemical Bonding using the octet rule as an explanatory principle is problematic in many ways. The aim of this case study is to understand the learning and teaching of Chemical Bonding using a research-informed teaching model in which Chemical Bonding is introduced as an electrostatic phenomenon. The study posed two main questions: (i) how does a student's understanding of Chemical Bonding evolve from lower- to upper-secondary school when an electrostatic model of Chemical Bonding was used at the lower-secondary level? (ii) How does the teaching of octets/full shells at the upper-secondary level affect students’ understanding? The same students were interviewed after lower-secondary school and again during their first year at upper-secondary school. Their upper-level chemistry teachers were also interviewed. The interview data were analysed using the grounded theory method. The findings showed that the students’ earlier proper understanding of the electrostatic-interactions model at the lower-secondary level did not prevent the later development of less-canonical thinking. Teachers’ pedagogical content knowledge (PCK) of the explanatory principles of Chemical Bonding and how to use explanations in science education needs to be promoted in both pre-service teacher education and during in-service training.
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coulombic interaction in finnish middle school chemistry a systemic perspective on students conceptual structure of Chemical Bonding
Chemistry Education Research and Practice, 2015Co-Authors: Jarkko Joki, Jari Lavonen, Kalle Juuti, Maija AkselaAbstract:The aim of this study was to design a novel and holistic way to teach Chemical Bonding at the middle school level according to research on the teaching and learning of Bonding. A further aim was to investigate high achieving middle school students' conceptual structures concerning Chemical Bonding by using a systemic perspective. Students in one metropolitan area middle school were introduced to this newly designed model and their conceptual structures were studied by a clinical interview (n = 8) at the time when the students were concluding their studies at the middle school. The interview data were analysed by employing a systemic perspective on conceptual structures. Elements of conceptual structures such as concepts, simple models (mnemonic devices), explaining schemas, attributes and hypothesis constructs were identified and coded. Connections between the knowledge elements were also identified. An understanding of these connections helps to illuminate which components are necessary to build an adequate conceptual structure. The study revealed that applying principles relating to Coulombic interaction to understand Chemical Bonding requires the simultaneous appreciation of several factors: First, electron shells have to be understood in terms of energy levels. Second, the distance between the outer electrons and the nucleus has to be understood on the basis of electron shell construction. On the other hand, the effective nuclear charge also needs to be taken into account. The study introduces two new points of view to chemistry education research (CER): (1) a teaching model of Chemical Bonding that emphasises electric interaction as the background of most Bonding types was developed in the study. This responds to the identified need in CER to test alternative teaching models that avoid the octet framework. (2) In the field of chemistry education research, a systemic approach has not previously been widely used for the examination of conceptual structures. In addition, the systemic perception of the network structure, which consists of these constructions, helps to explain in more detail the relationship between the separate concepts and the constructions and their significance as a whole.
Jing Feng - One of the best experts on this subject based on the ideXlab platform.
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stability Chemical Bonding behavior elastic properties and lattice thermal conductivity of molybdenum and tungsten borides under hydrostatic pressure
Ceramics International, 2016Co-Authors: Xiaoyu Chong, Yehua Jiang, Rong Zhou, Jing FengAbstract:Abstract The thermodynamic stability and mechanical properties of Mo–B and W–B binary compounds are investigated by first principles calculations and compared with other theoretical and experimental results. In order to determine the stability, compressive behavior and mechanical properties of Mo 2 B 5 and W 2 B 5 phases, hydrostatic pressure up to 10 GPa is applied to the crystal. The formation enthalpy, phonon spectrum, electronic structure and mechanical modulus at different pressure are obtained and variety of Chemical Bonding behavior has close relationship with the change of elastic properties. Temperature-dependent thermodynamics parameters of Mo 2 B 5 and W 2 B 5 are analyzed under different pressure. Moreover, the whole profile of temperature dependent lattice thermal conductivity of Mo 2 B 5 and W 2 B 5 from Debye temperature up to high temperature limit at different pressure is predicted by combining the Slack׳s, Clarke׳s and Cahill׳s model. The difference between the variation of lattice thermal conductivity of Mo 2 B 5 along [001] and [100] directions is attributed to the anisotropic Chemical Bonding behavior of B–B bonds and M–B bonds under pressure effect.
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mechanical properties and Chemical Bonding characteristics of wc and w2c compounds
Ceramics International, 2014Co-Authors: Yehua Jiang, Rong Zhou, Jing FengAbstract:Abstract The mechanical properties and Chemical Bonding features of W–C binary compounds (h-WC, o-W 2 C, h-W 2 C and t-W 2 C) were studied by density functional theory (DFT). It is shown that they are thermodynamically stable identified by the cohesive energy and formation enthalpy of W–C binary compounds. The elastic constants were calculated using the stress–strain method. The Voigt–Reuss–Hill approximation was used to evaluate the moduli. The surface constructions of bulk and Young's moduli were applied to illustrate the mechanical anisotropy. The population analysis of W–C binary compounds was used to discuss the Chemical Bonding, which indicate the combinations of covalent and metallic bonds in these compounds. Moreover, the anisotropic properties of sound velocities for W–C binary compounds were explored.
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mechanical properties and Chemical Bonding characteristics of cr7c3 type multicomponent carbides
Journal of Applied Physics, 2011Co-Authors: Bing Xiao, Yehua Jiang, Jing Feng, C T Zhou, Rong ZhouAbstract:The first principles calculations based on density functional theory are performed to investigate the mechanical properties and Chemical Bonding features of several Cr7C3 type multicomponent carbides (Fe16Cr12C12, Fe12Cr12W4C12, Fe12Cr12Mo4C12, Fe12Cr12W4C8B4, and Fe12Cr12Mo4C8B4). The full set elastic constants are calculated using stress-strain method. The Voigt–Reuss–Hill approximation is used to evaluate the mechanical moduli. The mechanical anisotropy is characterized by calculating several different anisotropic indexes and factors, such as universal anisotropic index (AU), shear anisotropic factors (A1, A2, and A3), and percent anisotropy (AB and AG). The surface constructions of bulk and Young’s moduli are illustrated to indicate the mechanical anisotropy. The obtained results indicate that the presence of B could deteriorate the mechanical moduli of (Fe,Cr)7C3 phase in Cr cast iron slightly. On the other hand, the Chemical stability of (Fe,Cr)7C3 carbides is improved due to Chemical Bonding modifi...
Nguyen Thanh Tung - One of the best experts on this subject based on the ideXlab platform.
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a dft investigation on geometry and Chemical Bonding of isoelectronic si 8 n 6 v si 8 n 6 cr and si 8 n 6 mn clusters
Chemical Physics Letters, 2017Co-Authors: Nguyen Minh Tam, Hung Tan Pham, Ngo Tuan Cuong, Nguyen Thanh TungAbstract:Abstract The geometric feature and Chemical Bonding of isoelectronic systems Si 8 N 6 M q (M = V, Cr, Mn and q = −1, 0, 1, respectively) are investigated by means of density-functional-theory calculations. The encapsulated form is found for all ground-state structures, where the metal atom locates at the central site of the hollow Si 8 N 6 cage. The Si 8 N 6 cage is established by adding two Si atoms to a distorted Si 6 N 6 prism, which is a combination of Si 4 N 2 and Si 2 N 4 strings. Chemical Bonding of Si 8 N 6 M q systems is explored by using the electron localization indicator and theory of atom in molecule, revealing the vital role of metal center in stabilizing the clusters.
Richard Dronskowski - One of the best experts on this subject based on the ideXlab platform.
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lobster a tool to extract Chemical Bonding from plane wave based dft
Journal of Computational Chemistry, 2016Co-Authors: Stefan Maintz, Volker L Deringer, A L Tchougreeff, Richard DronskowskiAbstract:The computer program LOBSTER (Local Orbital Basis Suite Towards Electronic-Structure Reconstruction) enables Chemical-Bonding analysis based on periodic plane-wave (PAW) density-functional theory (DFT) output and is applicable to a wide range of first-principles simulations in solid-state and materials chemistry. LOBSTER incorporates analytic projection routines described previously in this very journal [J. Comput. Chem. 2013, 34, 2557] and offers improved functionality. It calculates, among others, atom-projected densities of states (pDOS), projected crystal orbital Hamilton population (pCOHP) curves, and the recently introduced bond-weighted distribution function (BWDF). The software is offered free-of-charge for non-commercial research. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.
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analytic projection from plane wave and paw wavefunctions and application to Chemical Bonding analysis in solids
Journal of Computational Chemistry, 2013Co-Authors: Stefan Maintz, Volker L Deringer, A L Tchougreeff, Richard DronskowskiAbstract:Quantum-Chemical computations of solids benefit enormously from numerically efficient plane-wave (PW) basis sets, and together with the projector augmented-wave (PAW) method, the latter have risen to one of the predominant standards in computational solid-state sciences. Despite their advantages, plane waves lack local information, which makes the interpretation of local densities-of-states (DOS) difficult and precludes the direct use of atom-resolved Chemical Bonding indicators such as the crystal orbital overlap population (COOP) and the crystal orbital Hamilton population (COHP) techniques. Recently, a number of methods have been proposed to overcome this fundamental issue, built around the concept of basis-set projection onto a local auxiliary basis. In this work, we propose a novel computational technique toward this goal by transferring the PW/PAW wavefunctions to a properly chosen local basis using analytically derived expressions. In particular, we describe a general approach to project both PW and PAW eigenstates onto given custom orbitals, which we then exemplify at the hand of contracted multiple-ζ Slater-type orbitals. The validity of the method presented here is illustrated by applications to Chemical textbook examples-diamond, gallium arsenide, the transition-metal titanium-as well as nanoscale allotropes of carbon: a nanotube and the C60 fullerene. Remarkably, the analytical approach not only recovers the total and projected electronic DOS with a high degree of confidence, but it also yields a realistic Chemical-Bonding picture in the framework of the projected COHP method.
