The alloy theoretic automated toolkit: A user guide

Walle, Axel van de; Asta, Mark; Ceder, Gerbrand

doi:10.1016/s0364-5916(02)80006-2

Cited by 1,352 publications

(832 citation statements)

References 25 publications

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“…37 We have tested the case of (Fe, Zn)S 2 , using the initial structure generated by von Pezold et al 38 within the Alloy Theoretic Automated Toolkit (atat) code. 39 The ionically-relaxed mixing enthalpy obtained from the SQS approach is even higher than that obtained from the unit cell approach. Given that the mixing enthalpy ∆H obtained from the latter is already highly limiting for all systems, we have not carried out further investigations on the configurational effects using the SQS approach.…”

Section: Discussionmentioning

confidence: 81%

Feasibility of band gap engineering of pyrite FeS2

Sun

Ceder

2011

Phys. Rev. B

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We use first-principles computations to investigate whether the band gap of pyrite FeS2 can be increased by alloying in order to make it a more effective photovoltaic material. In addition to the isostructural compounds that have a larger band gap (ZnS2, RuS2, OsS2), we evaluate non-rareearth isovalent alloying candidates among all metals, transition metals, and semiconductor elements up to group IV and period 6 in the periodic table. From this screening procedure, we find that the group II elements (Be, Mg, Ca, Sr, Ba) and Cd have higher band gaps in the pyrite structure than FeS2. Practical band gap enhancement is observed only in the Ru and Os alloyed systems, but their incorporation into pyrite may be severely limited by the large positive enthalpy of mixing. All other candidate (Fe, M)S2 systems exhibit very large gap bowing effects such that the band gap at intermediate compositions is even lower than that of FeS2. Positive correlations between immiscibility and differences in electronegativity and Shannon ionic radius are observed.

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Section: Discussionmentioning

confidence: 81%

Feasibility of band gap engineering of pyrite FeS2

Sun

Ceder

2011

Phys. Rev. B

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“…For each volume, we used the socalled 'direct method' to obtain the phonon density of states. The lattice dynamics calculations used to determine the phonon density of states were performed using the ATAT code 34,35 , using supercells containing 32 atoms. From these calculations, the free energy (including contributions due to electronic degrees of freedom) can be easily calculated using the standard statistical mechanics formulas 6 .…”

Section: B Resultsmentioning

confidence: 99%

Finite-temperature elasticity of fcc Al: Atomistic simulations and ultrasonic measurements

et al. 2011

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Though not very often, in literature there are cases where discrepancies exist in temperature dependence of elastic constants of materials. A particular example of this case is the behavior of C 12 coefficient of a simple metal, aluminum. Here, we attempt to provide insight into various contributions to temperature-dependence in elastic properties by investigating the thermo-elastic properties of fcc aluminum as a function of temperature through the use of two computational techniques and experiments. First, ab initio calculations based on density functional theory (DFT) are used in combination with quasi-harmonic theory to calculate the elastic constants at finite temperatures through a strain-free energy approach. Molecular dynamics (MD) calculations using tight-binding potentials are then used to extract the elastic constants through a fluctuation-based formalism. Through this dynamic approach, the different contributions (Born, kinetic and stress fluctuations) to the elastic constants are isolated and the underlying physical basis for the observed thermally-induced softening is elucidated. The two approaches are then used to shed light on the relatively large discrepancies in the reported temperature dependence of the elastic constants of fcc aluminum. Finally, the polycrystalline elastic constants (and their temperature dependence) of fcc aluminum are determined using Resonant Ultrasound Spectroscopy (RUS) and compared to previously published data as well as the atomistic calculations performed in this work.

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“…To generate ground state structures, we use the Alloy Theoretic Automated Toolkit (ATAT) [8][9][10][11], a framework that iteratively generates a cluster expansion, based on abinitio total energies, to suggest new candidate ground state structures for a given lattice type.…”

Section: T=0k Binary Enthalpies Of Formationmentioning

confidence: 99%

Prediction of A2 to B2 Phase Transition in the High-Entropy Alloy Mo-Nb-Ta-W

Huhn

Widom

2013

JOM

101

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In this paper we show that an effective Hamiltonian fit with first principles calculations predicts an order/disorder transition occurs in the high entropy alloy MoNbTaW. Using the Alloy Theoretic Automated Toolset, we find T=0K enthalpies of formation for all binaries containing Mo, Nb, Ta, and W, and in particular we find the stable structures for binaries at equiatomic concentrations are close in energy to the associated B2 structure, suggesting that at intermediate temperatures a B2 phase is stabilized in MoNbTaW. Our previously published hybrid Monte Carlo/molecular dynamics results for the MoNbTaW system are analyzed to identify certain preferred chemical bonding types. A mean field free energy model incorporating nearest neighbor bonds is derived, allowing us to predict the mechanism of the order/disorder transition. We find the temperature evolution of the system is driven by strong Mo-Ta bonding. Comparison of the free energy model and our hybrid Monte Carlo/molecular dynamics results suggest the existence of additional low-temperature phase transitions in the system likely ending with phase segregation into binary phases. * wph@andrew.cmu.edu 2

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The alloy theoretic automated toolkit: A user guide

Cited by 1,352 publications

References 25 publications

Feasibility of band gap engineering of pyrite FeS2

Feasibility of band gap engineering of pyrite FeS2

Finite-temperature elasticity of fcc Al: Atomistic simulations and ultrasonic measurements

Prediction of A2 to B2 Phase Transition in the High-Entropy Alloy Mo-Nb-Ta-W

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