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Dallas R Trinkle - One of the best experts on this subject based on the ideXlab platform.
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ab initio magnesium solute transport database using exact diffusion theory
Acta Materialia, 2018Co-Authors: Ravi Agarwal, Dallas R TrinkleAbstract:Abstract A recently developed Green function approach informed by ab initio calculations models vacancy-mediated transport of 61 Solutes in a hexagonal close packed magnesium. The 8- and 13-frequency diffusion models approximate vacancy jump rates near a solute, leading to the inaccurate calculation of Onsager coefficients. We identify all the symmetry-unique vacancy jumps in the Mg lattice and use the Green function approach to calculate the Onsager coefficients exactly in the limit of dilute solute concentration. Density functional theory-computed solute-vacancy interactions and vacancy jump rates inform the Green function approach and previous diffusion models. Solutes with positive size misfit diffuse faster compared to the self-diffusion of Mg due to the relaxation of solute towards vacancy while Solutes with negative size misfit diffuse slower. Transition metal Solutes show drag for attractive solute-vacancy binding as well as for repulsive binding, due to faster reorientation rates of the vacancy around the solute compared to dissociation rates. Solutes from the s-block, p-block and lanthanide series with attractive solute-vacancy binding and slower reorientation rates compared to the dissociation rates show drag due to vacancy motion around the solute through alternate dissociation and association jumps. The prediction of activation energy of diffusion from the 8-frequency model deviates by more than 50 meV for Solutes with significant correlations effect. Our GF approach prediction of solute diffusion coefficients agree well with the available experimental measurements.
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Effect of Solutes on the lattice parameters and elastic stiffness coefficients of body-centered tetragonal Fe
Computational Materials Science, 2018Co-Authors: Michael R Fellinger, Louis G Hector, Dallas R TrinkleAbstract:Abstract We compute changes in the lattice parameters and elastic stiffness coefficients C ij of body-centered tetragonal (bct) Fe due to Al, B, C, Cu, Mn, Si, and N Solutes. Solute strain misfit tensors determine changes in the lattice parameters as well as strain contributions to the changes in the C ij . We also compute chemical contributions to the changes in the C ij , and show that the sum of the strain and chemical contributions agree with more computationally expensive direct calculations that simultaneously incorporate both contributions. Octahedral interstitial Solutes, with C being the most important addition in steels, must be present to stabilize the bct phase over the body-centered cubic phase. We therefore compute the effects of interactions between interstitial C Solutes and substitutional Solutes on the bct lattice parameters and C ij for all possible solute configurations in the dilute limit, and thermally average the results to obtain effective changes in properties due to each solute. The computed data can be used to estimate solute-induced changes in mechanical properties such as strength and ductility, and can be directly incorporated into mesoscale simulations of multiphase steels to model solute effects on the bct martensite phase.
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ab initio calculations of the lattice parameter and elastic stiffness coefficients of bcc fe with Solutes
Computational Materials Science, 2017Co-Authors: Michael R Fellinger, Louis G Hector, Dallas R TrinkleAbstract:Abstract We present an efficient methodology for computing solute-induced changes in lattice parameters and elastic stiffness coefficients C ij of single crystals using density functional theory. We introduce a solute strain misfit tensor that quantifies how Solutes change lattice parameters due to the stress they induce in the host crystal. Solutes modify the elastic stiffness coefficients through volumetric changes and by altering chemical bonds. We compute each of these contributions to the elastic stiffness coefficients separately, and verify that their sum agrees with changes in the elastic stiffness coefficients computed directly using fully optimized supercells containing Solutes. Computing the two elastic stiffness contributions separately is more computationally efficient and provides more information on solute effects than the direct calculations. We compute the solute dependence of polycrystalline averaged shear and Young’s moduli from the solute dependence of the single-crystal C ij . We apply this methodology to substitutional Al, B, Cu, Mn, Si Solutes and octahedral interstitial C and N Solutes in bcc Fe. Comparison with experimental data indicates that our approach accurately predicts solute-induced changes in the lattice parameter and elastic coefficients. The computed data can be used to quantify solute-induced changes in mechanical properties such as strength and ductility, and can be incorporated into mesoscale models to improve their predictive capabilities.
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first principles data for solid solution strengthening of magnesium from geometry and chemistry to properties
Acta Materialia, 2010Co-Authors: Joseph A Yasi, Louis G Hector, Dallas R TrinkleAbstract:Abstract Solid-solution strengthening results from Solutes impeding the glide of dislocations. Existing theories of strength rely on solute/dislocation interactions, but do not consider dislocation core structures, which need an accurate treatment of chemical bonding. Here, we focus on strengthening of Mg, the lightest of all structural metals and a promising replacement for heavier steel and aluminum alloys. Elasticity theory, which is commonly used to predict the requisite solute/dislocation interaction energetics, is replaced with quantum-mechanical first-principles calculations to construct a predictive mesoscale model for solute strengthening of Mg. Results for 29 different Solutes are displayed in a “strengthening design map” as a function of solute misfits that quantify volumetric strain and slip effects. Our strengthening model is validated with available experimental data for several Solutes, including Al and Zn, the two most common Solutes in Mg. These new results highlight the ability of quantum-mechanical first-principles calculations to predict complex material properties such as strength.
Michael H. Abraham - One of the best experts on this subject based on the ideXlab platform.
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analysis of solute pyridine intermolecular interactions based on experimental enthalpies of solution and enthalpies of solvation of Solutes dissolved in pyridine
Thermochimica Acta, 2018Co-Authors: Mikhail A Varfolomeev, Ilnaz T Rakipov, Ruslan N. Nagrimanov, Mikhail A Stolov, Michael H. AbrahamAbstract:Abstract In present work thermochemistry of solvation of inert gases and organic Solutes in pyridine was thoroughly studied using solution calorimetry technique. Enthalpies of solution at infinite dilution of 21 organic Solutes were determined experimentally at 298.15 K. Measured and literature data were analyzed using Acree and Abraham multi-parameter correlations for description of enthalpies of solvation. Both hydrogen bonding enthalpies between solute and pyridine in bulk pyridine and Gibbs energies of 1:1 complexation between solute and pyridine were calculated using solute and solvent descriptors. Obtained results are in good agreement with values calculated by previously proposed methods.
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prediction and mathematical correlation of the solubility of fluorene in alcohol solvents based upon the abraham general solvation model
Physics and Chemistry of Liquids, 2002Co-Authors: Cassandra I Monarrez, William E Acree, Michael H. AbrahamAbstract:The Abraham general solvation model is used to predict the saturation solubility of crystalline nonelectrolyte Solutes in organic solvents. The derived equations take the form of $$ \eqalign{ & \log (C_{\rm S} / C_{\rm W} ) = c + rR_2 + s\pi _2^{\rm H} + a\Sigma \alpha _2^{\rm H} + b\Sigma \beta _2^{\rm H} + vV_x \cr & \log (C_{\rm S} /C_{\rm G} ) = c + rR_2 + s\pi _2^{\rm H} + a\Sigma \alpha _2^{\rm H} + b\Sigma \beta _2^{\rm H} + l\log L^{16} \cr} $$ where C S and C W refer to the solute solubility in the organic solvent and water, respectively, C G is a gas phase concentration, R 2 is the solute's excess molar fraction, V x is McGowan volume of the solute, $\Sigma \alpha _2^{\rm H}$ and $\Sigma \beta _2^{\rm H}$ are measures of the solute's hydrogen-bond acidity and hydrogen-bond basicity, $\pi _2^{\rm H}$ denotes the solute's dipolarity/polarizability descriptor, and L 16 is the solute's gas phase dimensionless Ostwald partition coefficient into hexadecane at 298 K. The remaining symbols in the above ...
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hydrogen bonding xxxv relationship between high performance liquid chromatography capacity factors and water octanol partition coefficients
Journal of Chromatography A, 1994Co-Authors: Michael H. Abraham, Harpreet S Chadha, A LeoAbstract:Abstract The solvation equation log SP = c + rR2 + sπ2H + aΣα2H + bΣβ2H + vVx has been applied to reversed-phase HPLC capacity factors, as log k', for Solutes on a C18 bonded phase, with various water-methanoi mobile phases, using data by Yamagami and Takao. Here. SP is a property for a series of Solutes in a fixed solvent system, and the explanatory variables are solute descriptors as follows: R2, is an excess molar refraction, π2H is the solute dipolarity/polarizability, Σα2H and Σβ2H are the solute overall or effective hydrogen-bond acidity and basicity, and Vx, is the McGowan characteristic volume; c. r, s, a. h and v are constants. It is shown that the blend of factors that influence log k in any given system is not the same as that which influences log Poct. In particular, solute hydrogen-bond acidity considerably influences log k', but has no effect on log Poct. It follows that when log k' values are used to estimate log Poct. great care has to be taken to match the training set of Solutes in the correlation equation, with the Solutes for which log Poct is to be determined.
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hydrogen bonding 32 an analysis of water octanol and water alkane partitioning and the δlog p parameter of seiler
Journal of Pharmaceutical Sciences, 1994Co-Authors: Michael H. Abraham, Harpreet S Chadha, Gary S Whiting, Robert C MitchellAbstract:A general linear solvation energy equation has been used to analyze published partition coefficients in the systems water-octanol (613 Solutes), water-hexadecane (370 Solutes), water-alkane (200 Solutes), and water-cyclohexane (170 Solutes). The descriptors used in the equation are R2, an excess molar refraction; π2H, the solute dipolarity/polarizability; ∑α2H and ∑β2H, the effective solute hydrogen-bond acidity and basicity; and VX, the characteristic volume of McGowan. It is shown that the water-octanol partition coefficient is dominated by solute hydrogen-bond basicity, which favors water, and by solute size, which favors octanol, but solute excess molar refraction and dipolarity/polarizability are also significant. For the water-alkane partition coefficients, the same factors are at work, together with solute hydrogen-bond acidity as a major influence that favors water. An analysis of 288 Δlog P values shows that solute hydrogen-bond acidity is the major factor but that solute hydrogen-bond basicity and, to a lesser extent, solute dipolarity/polarizability and size are also significant factors that influence the Δlog P parameter.
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Hydrogen bonding. 32. An analysis of water-octanol and water-alkane partitioning and the Δlog p parameter of seiler
Journal of pharmaceutical sciences, 1994Co-Authors: Michael H. Abraham, Harpreet S Chadha, Gary S Whiting, Robert C MitchellAbstract:A general linear solvation energy equation has been used to analyze published partition coefficients in the systems water-octanol (613 Solutes), water-hexadecane (370 Solutes), water-alkane (200 Solutes), and water-cyclohexane (170 Solutes). The descriptors used in the equation are R2, an excess molar refraction; phi H2, the solute dipolarity/polarizability; sigma alpha H2 and sigma beta H2, the effective solute hydrogen-bond acidity and basicity; and Vx, the characteristic volume of McGowan. It is shown that the water-octanol partition coefficient is dominated by solute hydrogen-bond basicity, which favors water, and by solute size, which favors octanol, but solute excess molar refraction and dipolarity/polarizability are also significant. For the water-alkane partition coefficients, the same factors are at work, together with solute hydrogen-bond acidity as a major influence that favors water. An analysis of 288 delta log P values shows that solute hydrogen-bond acidity is the major factor but that solute hydrogen-bond basicity and, to a lesser extent, solute dipolarity/polarizability and size are also significant factors that influence the delta log P parameter.
Michael R Fellinger - One of the best experts on this subject based on the ideXlab platform.
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Effect of Solutes on the lattice parameters and elastic stiffness coefficients of body-centered tetragonal Fe
Computational Materials Science, 2018Co-Authors: Michael R Fellinger, Louis G Hector, Dallas R TrinkleAbstract:Abstract We compute changes in the lattice parameters and elastic stiffness coefficients C ij of body-centered tetragonal (bct) Fe due to Al, B, C, Cu, Mn, Si, and N Solutes. Solute strain misfit tensors determine changes in the lattice parameters as well as strain contributions to the changes in the C ij . We also compute chemical contributions to the changes in the C ij , and show that the sum of the strain and chemical contributions agree with more computationally expensive direct calculations that simultaneously incorporate both contributions. Octahedral interstitial Solutes, with C being the most important addition in steels, must be present to stabilize the bct phase over the body-centered cubic phase. We therefore compute the effects of interactions between interstitial C Solutes and substitutional Solutes on the bct lattice parameters and C ij for all possible solute configurations in the dilute limit, and thermally average the results to obtain effective changes in properties due to each solute. The computed data can be used to estimate solute-induced changes in mechanical properties such as strength and ductility, and can be directly incorporated into mesoscale simulations of multiphase steels to model solute effects on the bct martensite phase.
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ab initio calculations of the lattice parameter and elastic stiffness coefficients of bcc fe with Solutes
Computational Materials Science, 2017Co-Authors: Michael R Fellinger, Louis G Hector, Dallas R TrinkleAbstract:Abstract We present an efficient methodology for computing solute-induced changes in lattice parameters and elastic stiffness coefficients C ij of single crystals using density functional theory. We introduce a solute strain misfit tensor that quantifies how Solutes change lattice parameters due to the stress they induce in the host crystal. Solutes modify the elastic stiffness coefficients through volumetric changes and by altering chemical bonds. We compute each of these contributions to the elastic stiffness coefficients separately, and verify that their sum agrees with changes in the elastic stiffness coefficients computed directly using fully optimized supercells containing Solutes. Computing the two elastic stiffness contributions separately is more computationally efficient and provides more information on solute effects than the direct calculations. We compute the solute dependence of polycrystalline averaged shear and Young’s moduli from the solute dependence of the single-crystal C ij . We apply this methodology to substitutional Al, B, Cu, Mn, Si Solutes and octahedral interstitial C and N Solutes in bcc Fe. Comparison with experimental data indicates that our approach accurately predicts solute-induced changes in the lattice parameter and elastic coefficients. The computed data can be used to quantify solute-induced changes in mechanical properties such as strength and ductility, and can be incorporated into mesoscale models to improve their predictive capabilities.
Louis G Hector - One of the best experts on this subject based on the ideXlab platform.
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Effect of Solutes on the lattice parameters and elastic stiffness coefficients of body-centered tetragonal Fe
Computational Materials Science, 2018Co-Authors: Michael R Fellinger, Louis G Hector, Dallas R TrinkleAbstract:Abstract We compute changes in the lattice parameters and elastic stiffness coefficients C ij of body-centered tetragonal (bct) Fe due to Al, B, C, Cu, Mn, Si, and N Solutes. Solute strain misfit tensors determine changes in the lattice parameters as well as strain contributions to the changes in the C ij . We also compute chemical contributions to the changes in the C ij , and show that the sum of the strain and chemical contributions agree with more computationally expensive direct calculations that simultaneously incorporate both contributions. Octahedral interstitial Solutes, with C being the most important addition in steels, must be present to stabilize the bct phase over the body-centered cubic phase. We therefore compute the effects of interactions between interstitial C Solutes and substitutional Solutes on the bct lattice parameters and C ij for all possible solute configurations in the dilute limit, and thermally average the results to obtain effective changes in properties due to each solute. The computed data can be used to estimate solute-induced changes in mechanical properties such as strength and ductility, and can be directly incorporated into mesoscale simulations of multiphase steels to model solute effects on the bct martensite phase.
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ab initio calculations of the lattice parameter and elastic stiffness coefficients of bcc fe with Solutes
Computational Materials Science, 2017Co-Authors: Michael R Fellinger, Louis G Hector, Dallas R TrinkleAbstract:Abstract We present an efficient methodology for computing solute-induced changes in lattice parameters and elastic stiffness coefficients C ij of single crystals using density functional theory. We introduce a solute strain misfit tensor that quantifies how Solutes change lattice parameters due to the stress they induce in the host crystal. Solutes modify the elastic stiffness coefficients through volumetric changes and by altering chemical bonds. We compute each of these contributions to the elastic stiffness coefficients separately, and verify that their sum agrees with changes in the elastic stiffness coefficients computed directly using fully optimized supercells containing Solutes. Computing the two elastic stiffness contributions separately is more computationally efficient and provides more information on solute effects than the direct calculations. We compute the solute dependence of polycrystalline averaged shear and Young’s moduli from the solute dependence of the single-crystal C ij . We apply this methodology to substitutional Al, B, Cu, Mn, Si Solutes and octahedral interstitial C and N Solutes in bcc Fe. Comparison with experimental data indicates that our approach accurately predicts solute-induced changes in the lattice parameter and elastic coefficients. The computed data can be used to quantify solute-induced changes in mechanical properties such as strength and ductility, and can be incorporated into mesoscale models to improve their predictive capabilities.
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first principles data for solid solution strengthening of magnesium from geometry and chemistry to properties
Acta Materialia, 2010Co-Authors: Joseph A Yasi, Louis G Hector, Dallas R TrinkleAbstract:Abstract Solid-solution strengthening results from Solutes impeding the glide of dislocations. Existing theories of strength rely on solute/dislocation interactions, but do not consider dislocation core structures, which need an accurate treatment of chemical bonding. Here, we focus on strengthening of Mg, the lightest of all structural metals and a promising replacement for heavier steel and aluminum alloys. Elasticity theory, which is commonly used to predict the requisite solute/dislocation interaction energetics, is replaced with quantum-mechanical first-principles calculations to construct a predictive mesoscale model for solute strengthening of Mg. Results for 29 different Solutes are displayed in a “strengthening design map” as a function of solute misfits that quantify volumetric strain and slip effects. Our strengthening model is validated with available experimental data for several Solutes, including Al and Zn, the two most common Solutes in Mg. These new results highlight the ability of quantum-mechanical first-principles calculations to predict complex material properties such as strength.
Ken A. Dill - One of the best experts on this subject based on the ideXlab platform.
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Field-SEA: A Model for Computing the Solvation Free Energies
2016Co-Authors: Christopher J. Fennell, Ken A. DillAbstract:ABSTRACT: Previous work describes a computational solvation model called semi-explicit assembly (SEA). The SEA water model computes the free energies of solvation of nonpolar and polar Solutes in water with good efficiency and accuracy. However, SEA gives systematic errors in the solvation free energies of ions and charged Solutes. Here, we describe field-SEA, an improved treatment that gives accurate solvation free energies of charged Solutes, including monatomic and polyatomic ions and model dipeptides, as well as nonpolar and polar molecules. Field-SEA is computationally inexpensive for a given solute because explicit-solvent model simulations are relegated to a precomputation step and because it represents solvating waters in terms of a solute’s free-energy field. In essence, field-SEA approximates the physics of explicit-model simulations within a computationally efficient framework. A key finding is that an atom’s solvation shell inherits characteristics of a neighboring atom, especially strongly charged neighbors. Field-SEA may be useful where there is a need for solvation free-energy computations that are faster than explicit-solvent simulations and more accurate than traditional implicit-solvent simulations for a wide range of Solutes. 1
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Field-SEA: A Model for Computing the Solvation Free Energies of Nonpolar, Polar, and Charged Solutes in Water
2015Co-Authors: Christopher J. Fennell, Ken A. DillAbstract:Previous work describes a computational solvation model called semi-explicit assembly (SEA). The SEA water model computes the free energies of solvation of nonpolar and polar Solutes in water with good efficiency and accuracy. However, SEA gives systematic errors in the solvation free energies of ions and charged Solutes. Here, we describe field-SEA, an improved treatment that gives accurate solvation free energies of charged Solutes, including monatomic and polyatomic ions and model dipeptides, as well as nonpolar and polar molecules. Field-SEA is computationally inexpensive for a given solute because explicit-solvent model simulations are relegated to a precomputation step and because it represents solvating waters in terms of a solute’s free-energy field. In essence, field-SEA approximates the physics of explicit-model simulations within a computationally efficient framework. A key finding is that an atom’s solvation shell inherits characteristics of a neighboring atom, especially strongly charged neighbors. Field-SEA may be useful where there is a need for solvation free-energy computations that are faster than explicit-solvent simulations and more accurate than traditional implicit-solvent simulations for a wide range of Solutes
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potential of mean force between two hydrophobic Solutes in water
Biophysical Chemistry, 2002Co-Authors: Noel T Southall, Ken A. DillAbstract:We study the potential of mean force between two nonpolar Solutes in the Mercedes Benz model of water. Using NPT Monte Carlo simulations, we find that the solute size determines the relative preference of two solute molecules to come into contact ('contact minimum') or to be separated by a single layer of water ('solvent-separated minimum'). Larger Solutes more strongly prefer the contacting state, while smaller Solutes have more tendency to become solvent-separated, particularly in cold water. The thermal driving forces oscillate with solute separation. Contacts are stabilized by entropy, whereas solvent-separated solute pairing is stabilized by enthalpy. The free energy of interaction for small Solutes is well-approximated by scaled-particle theory.
