<i>Ab initio</i>determination of the atomistic structure of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Si</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ge</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mi>−</mml:mi><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>alloy

Venezuela, P.; Dalpian, Gustavo M.; Silva, Antônio J. R. da; Fazzio, A.

doi:10.1103/physrevb.64.193202

Cited by 60 publications

(35 citation statements)

References 26 publications

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“…These quasirandom structures optimize the arrangement of the M and N atoms for a given number of lattice sites, such that the structure as a whole mimics the lowest order correlation functions ͑pair and many body͒ of an infinite random alloy. [9][10][11] Hass et al 12 compared small ͑16 atom͒ SQS cells to the simulations of randomly distributed cations in supercells containing very large numbers of atoms ͑Ͼ500͒ and found that the density-functional theory ͑DFT͒ simulations based on the 16 atom SQS supercells adequately reproduced the dominant spectral features observed in the large supercell simulations. As we are not considering charged defects with large strain fields, minimum image effects are not expected to be an issue, therefore our supercells containing 64 atoms are deemed appropriate for this investigation.…”

Section: Modeling Random Alloysmentioning

confidence: 99%

Deviations from Vegard’s law in ternary III-V alloys

et al. 2010

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Vegard's law states that, at a constant temperature, the volume of an alloy can be determined from a linear interpolation of its constituent's volumes. Deviations from this description occur such that volumes are both greater and smaller than the linear relationship would predict. Here we use special quasirandom structures and density functional theory to investigate such deviations for M x N 1−x As ternary alloys, where M and N are group III species ͑B, Al, Ga, and In͒. Our simulations predict a tendency, with the exception of Al x Ga 1−x As, for the volume of the ternary alloys to be smaller than that determined from the linear interpolation of the volumes of the MAs and BAs binary alloys. Importantly, we establish a simple relationship linking the relative size of the group III atoms in the alloy and the predicted magnitude of the deviation from Vegard's law.

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Section: Modeling Random Alloysmentioning

confidence: 99%

Deviations from Vegard’s law in ternary III-V alloys

et al. 2010

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“…On the theoretical side, earlier ab initio theoretical calculations for Si 1-x Ge x alloys indicated a positive deviation from linearity, 11 in disagreement with the experimental results from Dismukes et al, 4 and with more recent calculations. 12,13 This suggests that convergence issues, as well as artificial correlations introduced by the small supercells used to simulate the alloy, may affect the predicted deviations from linearity. Accordingly, we have carried out ab initio lattice constant calculations in very large (1000 atom) supercells, which provide a statistically accurate description of the random alloy.…”

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Nonlinear structure-composition relationships in the Ge1−ySny/Si(100) (y<<

et al. 2011

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The compositional dependence of the cubic lattice parameter in Ge 1-y Sn y alloys has been revisited. Large 1000-atom supercell ab initio simulations confirm earlier theoretical predictions that indicate a positive quadratic deviation from Vegards' law, albeit with a somewhat smaller bowing coefficient, θ = 0.047 Å, than found from 64-atom cell simulations (θ = 0.063 Å). On the other hand, measurements from an extensive set of alloy samples with compositions y < 0.15 reveal a negative deviation from Vegard's law. The discrepancy with earlier experimental data, which supported the theoretical results, is traced back to an unexpected compositional dependence of the residual strain after growth on Si substrates. The experimental bowing parameter for the relaxed lattice constant of the alloys is found to be θ = -0.066 Å. Possible reasons for the disagreement between theory and experiment are discussed in detail.

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“…According to this definition a positive value of ⌬a͑x͒ corresponds to a negative bowing of the lattice parameter. 5 and DFT studies 6 based on the local density approximation ͑LDA͒. In Fig.…”

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confidence: 99%

“…10 The efficacy of this approach to describe the structure of random Si 1−x Ge x alloys has been demonstrated for a variety of systems. 6,7 The doping of Ge with isovalent atoms can be technologically important for the formation of radiation-hard devices. 11 Presently Sn 1−x Ge x alloys with low Sn content have been synthesized experimentally and here we will focus on these compounds.…”

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confidence: 99%

“…1,3 Although the structure and defect processes in diamondtype random alloys such as Si 1−x Ge x have received considerable attention, the structure of Sn 1−x Ge x has not, so far, been investigated in detail. [4][5][6][7][8] Previous density functional theory ͑DFT͒ studies were confined to predicting the structure of ordered Sn 1−x Ge x alloys. 9 Here we adopt the so-called special quasirandom structure ͑SQS͒ approach 10 to mimic the statistics of random Sn 1−x Ge x alloys at compositions x = 0.875, 0.75, and 0.625, respectively ͑see Fig.…”

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confidence: 99%

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