Theoretical Calculation of Absolute Radii of Atoms and Ions. Part 2. The Ionic Radii

Ghosh, Dulal C.; Biswas, Raka

doi:10.3390/i4060379

Cited by 81 publications

(47 citation statements)

References 29 publications

(32 reference statements)

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“…In the framework of DFT, this can be accomplished by noting the relationship between atomic charge, effective atomic size and atomic polarizability 24,51,53,54,77 . For example, since the Hubbard parameter is directly related to the chemical hardness (Eq.…”

Section: Theory and Methodsmentioning

confidence: 99%

A Modified QM/MM Hamiltonian with the Self-Consistent-Charge Density-Functional-Tight-Binding Theory for Highly Charged QM Regions

Hou

Zhu

Elstner

et al. 2012

J. Chem. Theory Comput.

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To improve the description of electrostatic interaction between QM and MM atoms when the QM is SCC-DFTB, we adopt a Klopman-Ohno (KO) functional form which considers the finite size of the QM and MM charge distributions. Compared to the original implementation that used a simple Coulombic interaction between QM Mulliken and MM point charges, the KO based QM/MM scheme takes charge penetration effect into consideration and therefore significantly improves the description of QM/MM interaction at short range, especially when the QM region is highly charged. To be consistent with the third-order formulation of SCC-DFTB, the Hubbard parameter in the KO functional is dependent on the QM charge. As a result, the effective size of the QM charge distribution naturally adjusts as the QM region undergoes chemical transformations, making the KO based QM/MM scheme particularly attractive for describing chemical reactions in the condensed phase. Together with the van der Waals parameters for the QM atom, the KO based QM/MM model introduces four parameters for each element type. They are fitted here based on microsolvation models of small solutes, focusing on negatively charged molecular ions, for elements O, C, H and P with a specific version of SCC-DFTB (SCC-DFTBPR). Test calculations confirm that the KO based QM/MM scheme significantly improves the interactions between QM and MM atoms over the original point charge based model and it is transferable due to the small number of parameters. The new form of QM/MM Hamiltonian will greatly improve the applicability of SCC-DFTB based QM/MM methods to problems that involve highly charged QM regions, such as enzyme catalyzed phosphoryl transfers.

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Section: Theory and Methodsmentioning

confidence: 99%

A Modified QM/MM Hamiltonian with the Self-Consistent-Charge Density-Functional-Tight-Binding Theory for Highly Charged QM Regions

Hou

Zhu

Elstner

et al. 2012

J. Chem. Theory Comput.

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“…Where: ρ = The sample density C p = The specific heat capacity [10] . For BaTiO 3 , the phase transformation from tetragonal to cubic structure occurs at 120~130°C [11] .…”

Section: Methodsmentioning

confidence: 99%

Effect of Sr Substitution on Structure and Thermal Diffusivity ofBa1-xSrxTiO3 Ceramic

Ridha¹,

Yunus²,

Halim³

et al. 2009

American J. of Engineering and Applied Sciences

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Problem statement:The aim of this research was to study the effect of Sr substitution on structure and thermal diffusivity of Ba l-x Sr x TiO 3 ceramic at room temperature. Approach: Structural and thermal diffusivity of Ba 1-x Sr x TiO 3 were studied by performing X-ray diffraction and photoflash measurements. The effects of Sr substitution on the structure and on the thermal diffusivity of Ba 1-x Sr x TiO 3 (0≤x≤1) were investigated. showed a significant effect of structure on thermo-physical property of materials.

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“…These ions prefer hard ligands but form weak complexes with them. However, the "soft" ions have greater affinity for "soft" sites and are more strongly bounded (Ghosh and Biswas, 2003;Liu et al, 2006;Puls and Bohn, 1988;Sparks, 1995). It should be noted that, at low pH values, Cr 6+ exists mainly as an oxyanion, which is adsorbed at positively charged sites.…”

Section: Batch Experimentsmentioning

confidence: 99%

Mobility of Cr, Pb, Cd, Cu and Zn in a loamy sand soil: A comparative study

et al. 2011

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Interest in soil contamination has been growing in recent years due to the ongoing degradation of soil environments. Therefore, the development of remediation techniques and the study of contaminant sorption and migration are areas of intense research. In this study, the authors sought to evaluate the scenario of co-contamination of a loamy sand soil by multiple heavy metals. To that end, the sorption and transport of five metals-Cr, Pb, Cd, Cu and Zn-was evaluated using representative samples of a soil from the north of Portugal. The tests were conducted in batch and continuous systems using single-and multiple-metal acid solutions to evaluate the effect of metal competition. In accordance with the type of assay-batch or continuous-Langmuir or Convection Dispersion Two-Site Nonequilibrium models were adjusted to explain the sorption/transport data. FTIR analyses were performed on the final samples of the continuous systems. Generally, the results revealed good fitting of the tested models for the metals in competitive and noncompetitive scenarios, with the exception of Zn that was originally present in soil samples at higher concentrations. As expected, the influence of competition was observed in both batch and continuous systems, but with different tendencies. The FTIR spectra also revealed a strong influence of clay minerals and organic matter on the sorption of the metals.

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Theoretical Calculation of Absolute Radii of Atoms and Ions. Part 2. The Ionic Radii

Abstract: Abstract:The theoretical method of determination of absolute atomic size, discussed in Int.J. Mol. Sci. 2002, 3, 87-113, is exploited to calculate absolute radii of the ions whose

Cited by 81 publications

References 29 publications

A Modified QM/MM Hamiltonian with the Self-Consistent-Charge Density-Functional-Tight-Binding Theory for Highly Charged QM Regions

A Modified QM/MM Hamiltonian with the Self-Consistent-Charge Density-Functional-Tight-Binding Theory for Highly Charged QM Regions

Effect of Sr Substitution on Structure and Thermal Diffusivity ofBa1-xSrxTiO3 Ceramic

Mobility of Cr, Pb, Cd, Cu and Zn in a loamy sand soil: A comparative study

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