Total energy pseudopotential calculation in local density approximation for BPO4

Site preference and the effects of ternary additions (Mn, V, etc.) on the twin energy in γ-TiAl were studied by means of all-electron total energy self-consistent calculations based on the local density approximation. The results show that when Mn, Ti, or V substitute on the Al-sites in γ-TiAl, the twin energy is about 20–25% lower than that of stoichiometric γ-TiAl; this may explain observations of increased twinning activity in 48% Al TiAl. By contrast, when ternary additions of V (or Al) occupy Ti-sites, the twin energy has nearly the same value as that of pure γ-TiAl, which is consistent with the observation of only a few twins for Al-rich compositions. By comparing the total energy of Ti6(XAl5) and (Ti5X)Al6 supercells, it is found that the relative stability of Ti6(XAl5) over (Ti5X)Al6 (i.e., the preference for occupying Al-sites) is increased in going from Nb, V, Cr, and Ti to Mn, in agreement with observation that excess Ti occupies Al-sites, and Nb preferentially substitutes on the Ti-sites. The results indicate that Mn preferentially substitutes on the Al-sites, and V (or Cr) may occupy both Ti- and Al-sites.

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Ab initio total energy studies of minerals using density functional theory and the local density approximation

Mineralogical Magazine ◽

10.1180/minmag.1995.059.397.02 ◽

1995 ◽

Vol 59 (397) ◽

pp. 589-596 ◽

Cited By ~ 11

Author(s):

Björn Winkler ◽

Victor Milman ◽

Michael C. Payne

Keyword(s):

Total Energy ◽

Ab Initio ◽

Local Density Approximation ◽

Density Functional ◽

Local Density ◽

Lattice Energy ◽

Density Approximation ◽

Proton Proton ◽

Energy Calculations ◽

Good Agreement

AbstractAb initio total energy calculations based on the local density approximation (LDA) and using a conjugate-gradient solver for the Kohn-Sham equations have been performed for cordierite, brucite, (Mg(OH)2) and diaspore (AlOOH). The calculated fractional coordinates of all structures are in good agreement with experimental diffraction data. The angle of the non-linear hydrogen bond in diaspore is reproduced well. The Raman active OH stretching frequency in brucite has been calculated using the frozen phonon approach and the calculated stretching frequency is in very good agreement with the observed value. The energetically most favourable calculated orientation of the proton-proton vector of an H2O molecule incorporated in the structural channels of cordierite agrees with findings deduced from spectroscopic data, and the calculated energy of hydration is in reasonable agreement with calorimetric data. It is therefore concluded that ab initio total energy calculations can confidently be used to predict properties of hydrogen bonded structures, which is difficult with conventional parameterized static lattice energy minimization calculations. An extension to the model is necessary to improve the agreement of the predicted to the observed lattice parameters for small structures.

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Defect Studies in Silicon Dioxide by Local Density Approximation Total Energy Methods

MRS Proceedings ◽

10.1557/proc-141-255 ◽

1988 ◽

Vol 141 ◽

Cited By ~ 5

Author(s):

Douglas C. Allan ◽

Michael P. Teter ◽

John D. Joannopoulos ◽

Yaneer Bar-Yam ◽

Sokrates T. Pantelides

Keyword(s):

Oxygen Vacancy ◽

Silicon Dioxide ◽

Total Energy ◽

Local Density Approximation ◽

Local Density ◽

Energy Methods ◽

Density Approximation ◽

Charge Densities ◽

Preliminary Results ◽

Total Energies

AbstractThe oxygen vacancy in silicon dioxide is currently believed to explain one of the most important defects observed in this material, the E1 ' center. To get a better understanding of the oxygen vacancy, we have investigated the equilibrium geometric structures, total energies, and charge densities of several charge states of the defect in alpha cristobalite. We also present some preliminary results for alpha quartz.

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