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Alfredo M. Simas - One of the best experts on this subject based on the ideXlab platform.
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Sparkle model for AM1 Calculation of neodymium(III) coordination compounds
Journal of Photochemistry and Photobiology A-chemistry, 2005Co-Authors: Cristiano C. Bastos, Ricardo O. Freire, Gerd B. Rocha, Alfredo M. SimasAbstract:Abstract The Sparkle/AM1 model, the only available semiempirical quantum chemical model for the Calculation of complexes of lanthanide ions, recently defined for Eu(III), Gd(III) and Tb(III), is now extended to Nd(III). Accordingly, all 57 Nd(III) complexes of high crystallographic quality ( R -factor
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Sparkle model for the AM1 Calculation of dysprosium (III) complexes
Inorganic Chemistry Communications, 2005Co-Authors: Nivan B. Da Costa, Ricardo O. Freire, Gerd B. Rocha, Alfredo M. SimasAbstract:Abstract The Sparkle/AM1 model, recently defined for Eu(III), Gd(III) and Tb(III) [R.O. Freire, G.B. Rocha, A.M. Simas, Inorg. Chem. 44 (2005) 3299] is extended to Dy(III) complexes, using the same parameterization scheme. Thus, a set of 15 complexes, with various representative ligands of high crystallographic quality (R-factor
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Sparkle Model for AM1 Calculation of Lanthanide Complexes: Improved Parameters for Europium†
Inorganic chemistry, 2004Co-Authors: Gerd B. Rocha, Ricardo O. Freire, Nivan B. Da Costa, Alfredo M. SimasAbstract:In the present work, we sought to improve our sparkle model for the Calculation of lanthanide complexes, SMLC, in various ways: (i) inclusion of the europium atomic mass, (ii) reparametrization of the model within AM1 from a new response function including all distances of the coordination polyhedron for tris(acetylacetonate)(1,10-phenanthroline) europium(III), (iii) implementation of the model in the software package MOPAC93r2, and (iv) inclusion of spherical Gaussian functions in the expression which computes the core−core repulsion energy. The parametrization results indicate that SMLC II is superior to the previous version of the model because Gaussian functions proved essential if one requires a better description of the geometries of the complexes. In order to validate our parametrization, we carried out Calculations on 96 europium(III) complexes, selected from Cambridge Structural Database 2003, and compared our predicted ground state geometries with the experimental ones. Our results show that th...
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sparkle model for the quantum chemical AM1 Calculation of europium complexes of coordination number nine
Journal of Alloys and Compounds, 1995Co-Authors: Antônio V.m. De Andrade, Nivan B. Da Costa, Alfredo M. SimasAbstract:Abstract Recently, we have proposed the representation of lanthanides within AM1 as sparkles for the purpose of obtaining ground state geometries of their complexes. In the present work we tested our quantum chemical sparkle model for the prediction of the crystallographic structure of tris (dipivaloylmethanato) (2,2′:6′,2′'-terpyridine) of europium(III), a complex with coordination number nine. Considering the coordination polyhedron, the interatomic distances averaging 2.83 A and the bond angles could be predicted with an average deviation of 0.12 A and 5° respectively. This finding reinforces our model and consequently the notion that the lanthanide-ligand interaction is essentially electrostatic.
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Sparkle model for the quantum chemical AM1 Calculation of europium complexes
Chemical Physics Letters, 1994Co-Authors: Antônio V.m. De Andrade, Nivan B. Da Costa, Alfredo M. SimasAbstract:Abstract Considering that the bonds between a lanthanide and its ligands essentially possess an electrostatic character, we propose the representation of rare-earth elements within AM1 as sparkles. To parametrize the sparkle model we have used the known geometry of the complex tris (acetylacetonate) (1,10-phenantroline) of europium (III). Interatomic distances for the coordination polyhedron, averaging 2.81 A, could be predicted with an average deviation of 0.13 A. In short, this is a simple lanthanide-ligand electrostatic model which simultaneously treats the organic ligands and their interactions with the powerful AM1 method, yielding results of useful accuracy.
Nivan B. Da Costa - One of the best experts on this subject based on the ideXlab platform.
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Sparkle model for the AM1 Calculation of dysprosium (III) complexes
Inorganic Chemistry Communications, 2005Co-Authors: Nivan B. Da Costa, Ricardo O. Freire, Gerd B. Rocha, Alfredo M. SimasAbstract:Abstract The Sparkle/AM1 model, recently defined for Eu(III), Gd(III) and Tb(III) [R.O. Freire, G.B. Rocha, A.M. Simas, Inorg. Chem. 44 (2005) 3299] is extended to Dy(III) complexes, using the same parameterization scheme. Thus, a set of 15 complexes, with various representative ligands of high crystallographic quality (R-factor
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Sparkle Model for AM1 Calculation of Lanthanide Complexes: Improved Parameters for Europium†
Inorganic chemistry, 2004Co-Authors: Gerd B. Rocha, Ricardo O. Freire, Nivan B. Da Costa, Alfredo M. SimasAbstract:In the present work, we sought to improve our sparkle model for the Calculation of lanthanide complexes, SMLC, in various ways: (i) inclusion of the europium atomic mass, (ii) reparametrization of the model within AM1 from a new response function including all distances of the coordination polyhedron for tris(acetylacetonate)(1,10-phenanthroline) europium(III), (iii) implementation of the model in the software package MOPAC93r2, and (iv) inclusion of spherical Gaussian functions in the expression which computes the core−core repulsion energy. The parametrization results indicate that SMLC II is superior to the previous version of the model because Gaussian functions proved essential if one requires a better description of the geometries of the complexes. In order to validate our parametrization, we carried out Calculations on 96 europium(III) complexes, selected from Cambridge Structural Database 2003, and compared our predicted ground state geometries with the experimental ones. Our results show that th...
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sparkle model for the quantum chemical AM1 Calculation of europium complexes of coordination number nine
Journal of Alloys and Compounds, 1995Co-Authors: Antônio V.m. De Andrade, Nivan B. Da Costa, Alfredo M. SimasAbstract:Abstract Recently, we have proposed the representation of lanthanides within AM1 as sparkles for the purpose of obtaining ground state geometries of their complexes. In the present work we tested our quantum chemical sparkle model for the prediction of the crystallographic structure of tris (dipivaloylmethanato) (2,2′:6′,2′'-terpyridine) of europium(III), a complex with coordination number nine. Considering the coordination polyhedron, the interatomic distances averaging 2.83 A and the bond angles could be predicted with an average deviation of 0.12 A and 5° respectively. This finding reinforces our model and consequently the notion that the lanthanide-ligand interaction is essentially electrostatic.
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Sparkle model for the quantum chemical AM1 Calculation of europium complexes
Chemical Physics Letters, 1994Co-Authors: Antônio V.m. De Andrade, Nivan B. Da Costa, Alfredo M. SimasAbstract:Abstract Considering that the bonds between a lanthanide and its ligands essentially possess an electrostatic character, we propose the representation of rare-earth elements within AM1 as sparkles. To parametrize the sparkle model we have used the known geometry of the complex tris (acetylacetonate) (1,10-phenantroline) of europium (III). Interatomic distances for the coordination polyhedron, averaging 2.81 A, could be predicted with an average deviation of 0.13 A. In short, this is a simple lanthanide-ligand electrostatic model which simultaneously treats the organic ligands and their interactions with the powerful AM1 method, yielding results of useful accuracy.
Antônio V.m. De Andrade - One of the best experts on this subject based on the ideXlab platform.
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sparkle model for the quantum chemical AM1 Calculation of europium complexes of coordination number nine
Journal of Alloys and Compounds, 1995Co-Authors: Antônio V.m. De Andrade, Nivan B. Da Costa, Alfredo M. SimasAbstract:Abstract Recently, we have proposed the representation of lanthanides within AM1 as sparkles for the purpose of obtaining ground state geometries of their complexes. In the present work we tested our quantum chemical sparkle model for the prediction of the crystallographic structure of tris (dipivaloylmethanato) (2,2′:6′,2′'-terpyridine) of europium(III), a complex with coordination number nine. Considering the coordination polyhedron, the interatomic distances averaging 2.83 A and the bond angles could be predicted with an average deviation of 0.12 A and 5° respectively. This finding reinforces our model and consequently the notion that the lanthanide-ligand interaction is essentially electrostatic.
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Sparkle model for the quantum chemical AM1 Calculation of europium complexes
Chemical Physics Letters, 1994Co-Authors: Antônio V.m. De Andrade, Nivan B. Da Costa, Alfredo M. SimasAbstract:Abstract Considering that the bonds between a lanthanide and its ligands essentially possess an electrostatic character, we propose the representation of rare-earth elements within AM1 as sparkles. To parametrize the sparkle model we have used the known geometry of the complex tris (acetylacetonate) (1,10-phenantroline) of europium (III). Interatomic distances for the coordination polyhedron, averaging 2.81 A, could be predicted with an average deviation of 0.13 A. In short, this is a simple lanthanide-ligand electrostatic model which simultaneously treats the organic ligands and their interactions with the powerful AM1 method, yielding results of useful accuracy.
Sun Wei - One of the best experts on this subject based on the ideXlab platform.
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Study of ion cluster reorientation process of geopolymerisation reaction using semi-empirical AM1 Calculations
Cement and Concrete Research, 2009Co-Authors: Zhang Yunsheng, Sun Wei, Jia Yantao, Li ZongjinAbstract:In this paper all the possible reaction pathways involved in ion clusters reorientation process of metakaolin based Geopolymeric cement were systemically investigated according to thermodynamic theory. The reaction energy of every possible reorientation pathway was also calculated using computational chemistry method-semi-empirical AM1 Calculation. The optimum reorientation pathway was analyzed based on the energy-minimized principle. The Calculation results showed that Si-Al hybrid reorientation should be primary reorientation pathway of Geopolymeric cement made with NaOH or KOH activated metakaolin. This viewpoint was also verified by Nuclear Magnetic Resonance Spectroscopy equipped with Magic Angle Spinning technique (MAS-NMR). In addition, the semi-empirical AM1 Calculations revealed that the reorientation reaction is easier and stronger in NaOH solution than in KOH solution.
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Semi-empirical AM1 Calculations on 6-memebered alumino-silicate rings model: implications for dissolution process of metakaoline in alkaline solutions
Journal of Materials Science, 2007Co-Authors: Zhang Yunsheng, Sun WeiAbstract:In order to investigate the dissolution process of metakaline in alkaline solutions, two 6-memebered rings models consisting of AlO4 tetrahedron and SiO4 tetrahedron, respectively are firstly proposed to represent the structure of metakaoline in this paper. Analysis of the dissolution mechanism of the two 6-memebered rings models in strongly solution reveals that the dissolution process of metakaoline is composed of ring breakage for releasing HOTO3≡ anion, formation of HO–T(OM)3 by ion-pairing reaction between HOTO3≡ anion and M+ cation, and further interaction between the remaining broken ring cluster and MOH solutions. A computational chemistry method: Semi-empirical AM1 Calculation is then conducted on the two models to obtain the details of three steps involved in dissolution process. The calculated results showed that 6-member ring model consisting of AlO4 tetrahedron is more reactive than 6-member ring model consisting of SiO4 tetrahedron. Compared with local environment, strongly alkaline accelerated the dissolution of 6-member ring model consisting of SiO4 tetrahedron. Na+ has stronger ion-pairing interaction than K+. The further reaction between the remaining broken ring cluster and strongly alkaline solution depended on the types of the remaining broken ring cluster and alkaline solution. The above results enhanced our understanding of dissolution mechanisms of metakaoline in highly alkaline solutions, which is especially important to geopolymerization reaction.
Zhang Yunsheng - One of the best experts on this subject based on the ideXlab platform.
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Study of ion cluster reorientation process of geopolymerisation reaction using semi-empirical AM1 Calculations
Cement and Concrete Research, 2009Co-Authors: Zhang Yunsheng, Sun Wei, Jia Yantao, Li ZongjinAbstract:In this paper all the possible reaction pathways involved in ion clusters reorientation process of metakaolin based Geopolymeric cement were systemically investigated according to thermodynamic theory. The reaction energy of every possible reorientation pathway was also calculated using computational chemistry method-semi-empirical AM1 Calculation. The optimum reorientation pathway was analyzed based on the energy-minimized principle. The Calculation results showed that Si-Al hybrid reorientation should be primary reorientation pathway of Geopolymeric cement made with NaOH or KOH activated metakaolin. This viewpoint was also verified by Nuclear Magnetic Resonance Spectroscopy equipped with Magic Angle Spinning technique (MAS-NMR). In addition, the semi-empirical AM1 Calculations revealed that the reorientation reaction is easier and stronger in NaOH solution than in KOH solution.
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Semi-empirical AM1 Calculations on 6-memebered alumino-silicate rings model: implications for dissolution process of metakaoline in alkaline solutions
Journal of Materials Science, 2007Co-Authors: Zhang Yunsheng, Sun WeiAbstract:In order to investigate the dissolution process of metakaline in alkaline solutions, two 6-memebered rings models consisting of AlO4 tetrahedron and SiO4 tetrahedron, respectively are firstly proposed to represent the structure of metakaoline in this paper. Analysis of the dissolution mechanism of the two 6-memebered rings models in strongly solution reveals that the dissolution process of metakaoline is composed of ring breakage for releasing HOTO3≡ anion, formation of HO–T(OM)3 by ion-pairing reaction between HOTO3≡ anion and M+ cation, and further interaction between the remaining broken ring cluster and MOH solutions. A computational chemistry method: Semi-empirical AM1 Calculation is then conducted on the two models to obtain the details of three steps involved in dissolution process. The calculated results showed that 6-member ring model consisting of AlO4 tetrahedron is more reactive than 6-member ring model consisting of SiO4 tetrahedron. Compared with local environment, strongly alkaline accelerated the dissolution of 6-member ring model consisting of SiO4 tetrahedron. Na+ has stronger ion-pairing interaction than K+. The further reaction between the remaining broken ring cluster and strongly alkaline solution depended on the types of the remaining broken ring cluster and alkaline solution. The above results enhanced our understanding of dissolution mechanisms of metakaoline in highly alkaline solutions, which is especially important to geopolymerization reaction.
