User talk:Logger9

DFT Rewrite

Source

A quantitative structure-property relationship (QSPR) model obtained by using multiple linear stepwise regression analysis, with correlation coefficient R of 0.979 for the training set and 0.951 for the validation set, was developed to predict the glass transition temperature (T g) values of polyacrylates. Three quantum chemical descriptors (the molecular average polarizability a, the entropy S, and the lowest unoccupied molecular orbital E LUMO) obtained directly from polyacrylates monomer structure by density function theory (DFT) calculation, were used to produce the model. The result confirmed the role that quantum chemical descriptors play in studying QSPR of glass transition temperature for polymers.

Logger9

a quantitative structure-property relationship (QSPR) model was obtained through the use of multiple linear stepwise regression analysis. This work used a correlation coefficient R of 0.979 for the training set, while an R value of 0.951 was used for the validation set. The model was developed in order to predict the glass transition temperature values of several polyacrylates. Three quantum chemical descriptors -- the molecular average polarizability a, the entropy S, and the lowest unoccupied molecular orbital (ELUMO) -- were obtained from monomer structures by using density function theory (DFT) calculations. These descriptors were then used in order to produce the model. The result confirmed the primary role of such descriptors in studying QSPR models of the Tg for these polymers.

Source

density functional theory (DFT) calculations for 60 polyvinyls, polyethylenes and polymethacrylates repeating units at the B3LYP/6-31G(d) level, two quantum chemical descriptors, the molecular traceless quadrupole moment T, the molecular average hexadecapole moment F, are obtained and used to predict the glass transition temperature (Tg)

Logger9

density functional theory (DFT) calculations for 60 polyvinyls, polyethylenes and polymethacrylates, two quantum chemical descriptors (the molecular traceless quadrupole moment T and the molecular average hexadecapole moment F) are obtained. These descriptors are than used in order to predict Tg

Source

The glass transition of a hard sphere system is investigated within the framework of the density functional theory (DFT). Molecular dynamics (MD) simulations are performed to study the dynamical behavior of the system on the one hand and to provide the data to produce the density field for the DFT on the other hand. Energy landscape analysis based on the DFT shows that there appears a metastable (local) free energy minimum representing an amorphous state as the density is increased. This state turns out to become stable, compared with the uniform liquid, at some density around which we also observe a sharp slowing down of the alpha relaxation in the MD simulations.

Logger9

The glass transition of a hard sphere system has been investigated within the framework of the density functional theory (DFT). Molecular dynamics (MD) simulations are performed in order to study the dynamical behavior of the system as well as to provide data to produce the density field for the DFT. Energy landscape analysis based on the DFT shows indicates a metastable (local) free energy minimum. The minimum in F is representative of an amorphous state as the density is increased. This state turns out to become stabilized thermodynamically compared with the uniform liquid at some density value around which there is also observed a distinct slowing down of the relaxation in the MD simulations.

Source

Glasses and glass ceramics in the ternary xEu2O3·(100 - x)[7TeO2·3P2O5] systems .. have been prepared from melt quenching method. Influence of europium ions on structural behavior in phosphate–tellurate glasses has been investigated using infrared spectroscopy. The addition of high Eu2O3 content resulted in gradual depolymerization of the phosphate chains and formation of the EuPO4 crystalline phase. Presence of the multiple cations of europium and tellurium in the glasses to attract the [PO4] structural units

Comparing the theoretical and experimental IR spectral characteristic features, we conclude that the performance of the method/basis sets used on the prediction of the structural data and vibrational modes is good.

Logger9

glasses as well as glass ceramics in the ternary Eu2O3·7TeO2·3P2O5 system which have been prepared utilizing the melt quenching method. The influence of europium ions on microstructural behavior in phosphate-tellurate glasses has been investigated using IR spectroscopy. The addition of high Eu2O3 content resulted in gradual depolymerization of the phosphate chains. An additional effect included the formation of the EuP04 crystalline phase. The presence of multiple cations of europium and tellurium in these compounds tends to attract the [PO4] structural units

Comparison between theory and experiment here is good, as it was concluded that the performance of the method/basis sets used on the prediction of the structural data and vibrational modes is good

Source

Raman spectra have been interpreted using density functional theory (DFT) harmonic frequency calculations on specific clusters of GaS4H4 and/or GaS3H3Cl tetrahedral subunits. The assignment of the observed vibrational bands confirms the main structural conclusions obtained with X-ray and neutron diffraction experiments

however, no Raman signature of chlorine-doped subunits has been found to be caused by their insufficient intensity. For higher CsCl concentrations, distinct spectral features corresponding to chlorine-doped clusters appear

The added chlorine atoms induce a fragmentation of the glass network and replace the sulfur atoms in the CS tetrahedral environment. The comparison of the observed spectra with theoretical predictions and diffraction data favoured one-fold coordinated chlorine atoms in the glass network.

Logger9

Raman spectra have then been interpreted by application of harmonic frequency DFT calculations on specific clusters of GaS4H4 and/or GaS3H3Cl tetrahedral substrucural units. The assignment of the observed vibrational bands confirms the main structural conclusions which have been obtained in X-ray and neutron diffraction experiments.

However, no Raman signature of chlorine-doped subunits has been found, which may be caused by their lack of intensity..for higher CsCl concentrations, distinct spectral features which are typically associated with chlorine-doped clusters appear

The added chlorine atoms thus appears to induce a fragmentation of the glassy network by replacing the sulfur atoms in the CS tetrahedral environment. The comparison of the observed Raman spectra with theoretical DFT predictions and diffraction data tends to favor a 1-fold coordination for chlorine atoms within the glassy network.

Source

The local structures of two metallic glasses with good plasticity, i.e., Al89La6Ni5 and Cu49Hf42Al9, were studied by reduced density functions (RDFs) from electron diffraction in a transmission electron microscope. Atomic models were refined against the RDF data using the reverse Monte Carlo (RMC) method and density functional theory (DFT) calculations. This approach allows the contributions of different bond types to the total G(r) to be examined. For Al89La6Ni5, RDFs from different local areas showed three distinct amorphous structures while RDFs from different local areas in Cu49Hf42Al9 were identical, but with a broad spread of Hf-Hf bond lengths. The coexistence of three distinct amorphous states in Al89La6Ni5 and the wide variation of Hf-Hf first neighbour distances in Cu49Hf42Al9 could be associated with the high plasticity for both glasses.

Logger9

The local structures of two metallic glasses with good plasticity, i.e., Al89La6Ni5 and Cu49Hf42Al9, were studied by using reduced density functions (RDFs) from electron diffraction in a transmission electron microscope (TEM). Atomic models were refined against the RDF data using the reverse Monte Carlo (RMC) method and density functional theory (DFT) calculations. This approach allows the comparison of different types of metallic bonding to the total G(r.) For RDFs from the Al89La6Ni5 alloy composition, different local areas showed three distinct amorphous structures. RDFs from different local areas in the Cu49Hf42Al9 alloy composition were identical. But interestingly, these samples showed a broad spread of Hf-Hf bond lengths. Both of these results could be associated with the high plasticity for both of these metallic glasses.

New version

Applicable work in the field of DFT has been abundant over the last several years. In particular, one model was developed in order to predict the glass transition temperature T_g values of several polyacrylates ^[1] as well as other polymers, including 60 polyvinyls, polyethylenes and polymethacrylates ^[2] In addition, The glass transition of a hard sphere system has been investigated, where Molecular dynamics (MD) simulations have been utilized in order to study the dynamical behavior of the system. In these studies, a minimum in the free energy landscape is representative of an amorphous state as the density is increased. The stability of this state becomes evident as compared with the uniform liquid. This occurs at some density value whic corresponds with a distinct slowing down of the relaxation in the MD simulations. ^[3]

DFT calcualations have been carried out on glasses as well as glass ceramics in the ternary u₂O₃·7TeO₂·3P₂O₅ system which have been prepared utilizing the melt quenching method. In these studies, the influence of europium ions on microstructural behavior in phosphate-tellurate glasses has been investigated using IR spectroscopy. IR changes attribute the influence[PO₄] microstructural units in helping to explain a drastic reduction of the characteristic features corresponding to bandwidth, position and intensity. ^[4] In another study, several vanadate-tellurate vitreous systems were prepared by using the conventional method of melt quenching. Microstructural features have been investigated using FTIR spectroscopy as well as density functional theory (DFT) calculations. ^[5]

The alkali metal halide doping of gallium-sulfide glasses has been shown to optimize both optical and thermal properties, as well as enhancing the glass forming capacity of these compounds. ^[6] One group used DFT in order to calculate the structure, bond length (picometer, pm), and vibrational frequencies(intensities)[degeneracy] for various clusters of arsenic selenide. It was confirmed in these studies that linear As-Se-As -- for which the calculated fundamental vibrational frequency is 27.6 cm^-1 -- is in agreement with the data of Nemanich (Phys. Rev. B, Vol. 16, p. 1655, 1977), and J.C. Phillips, et al., (Phys. Rev B, Vol. 21, p. 5724,1980). The same group have also successfully calculated several higher (harmonic or overtone) vibrational frequencies. Interestingly, these data are in excellent agreement with the Raman data in the same system [J. Non-Cryst. Solids, Vol. 351, 489(2005); Vol., 353, 111, 2007]. ^[7]

Finally, the local structures of two metallic glasses with good plasticity, i.e., Al₈₉La₆Ni₅ and Cu₄₉Hf₄₂A_l9, were studied by using reduced density functions (RDFs) from electron diffraction in a transmission electron microscope (TEM). Atomic models were refined against the RDF data using the reverse Monte Carlo (RMC) method and density functional theory (DFT) calculations. These samples showed a broad spread of Hf-Hf bond lengths, which could be associated with the high plasticity for both of these metallic glasses. ^[8]

References

Comparison

Logger, your new version is still a clear copyright violation. Compare your final paragraph with the source you claim above to have paraphrased it from (identical phrases are in bold):

Finally, the local structures of two metallic glasses with good plasticity, i.e., Al89La6Ni5 and Cu49Hf42Al9, were studied by using reduced density functions (RDFs) from electron diffraction in a transmission electron microscope (TEM). Atomic models were refined against the RDF data using the reverse Monte Carlo (RMC) method and density functional theory (DFT) calculations. These samples showed a broad spread of Hf-Hf bond lengths, which could be associated with the high plasticity for both of these metallic glasses.

The fact that you can't manage to write a few non-plagiarised paragraphs when you're attempting to demonstrate your reformed character in the middle of a copyright investigation is concerning. Djr32 (talk) 11:46, 3 January 2011 (UTC)