Special quasirandom structures

Zunger, Alex; Wei, Su‐Huai; Ferreira, L. G.; Bernard, J. E.

doi:10.1103/physrevlett.65.353

Cited by 3,172 publications

(1,895 citation statements)

References 17 publications

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“…Special quasirandom structures (SQS) are commonly used to simulate the structure of a random alloy using a small supercell (typically 2 × 2 × 2) whose correlation function closely approximates that of an ideal random alloy for a given concentration. 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.…”

Section: Discussionmentioning

confidence: 99%

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: 99%

Feasibility of band gap engineering of pyrite FeS2

Sun

Ceder

2011

Phys. Rev. B

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“…The disordered state was modelled by a special quasirandom structure (SQS) [37]. The SQSs are small unit cell structures that are constructed to mimic the short-range correlations of a truly random structure as much as possible.…”

Section: First-principles Study Of Pd 3 Vmentioning

confidence: 99%

Vibrational thermodynamics: coupling of chemical order and size effects

Morgan¹,

Walle²,

Ceder³

et al. 2000

Modelling Simul. Mater. Sci. Eng.

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Abstract. The effects of chemical order on the vibrational entropy have been studied using firstprinciples and semi-empirical potential methods. Pseudopotential calculations on the Pd 3 V system show that the vibrational entropy decreases by 0.07k B upon disordering in the high-temperature limit. The decrease in entropy contradicts what would be expected from simple bonding arguments, but can be explained by the influence of size effects on the vibrations. In addition, the embeddedatom method is used to study the effects of local environments on the entropic contributions of individual Ni and Al atoms in Ni 3 Al. It is found that increasing numbers of Al nearest neighbours decreases the vibrational entropy of an atom when relaxations are not included. When the system is relaxed, this effect disappears, and the local entropy is approximately uniform with increasing number of Al neighbours. These results are explained in terms of the large size mismatch between Ni and Al. In addition, a local cluster expansion is used to show how the relaxations increase the importance of long-range and multisite interactions.

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“…In most materials, local magnetic moments do survive above the magnetic transition temperature, and hence a proper treatment of magnetic disorder is essential for the predictive description and exploration of materials properties, especially close to the order-disorder transition temperature, the Curie T C or Néel T N for FM and AFM materials, respectively [91]. An approach used to model the PM state of MAX phases [7,10,28] is the disordered local moments (DLM) method [92] where a solid solution with 50% up and 50% down spins on the M sublattice is simulated using the special quasi-random structures (SQS) method [93]. For Mn-containing MAX phases, such as (Cr 0.5 Mn 0.5 ) 2 AlC [7] and Mn 2 GaC [28], the DLM method works with sustained disorder and non-zero local magnetic moments after electronic relaxation.…”

Section: Identification Of Magnetic Ground-statementioning

confidence: 99%

Magnetic MAX phases from theory and experiments; a review

Ingason

Dahlqvist

Rosén

2016

J. Phys.: Condens. Matter

109

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This review presents MAX phases (M is a transition metal, A an A-group element, X is C or N), known for their unique combination of ceramic/metallic properties, as a recently uncovered family of novel magnetic nanolaminates. The first created magnetic MAX phases were predicted using density functional theory through evaluation of phase stability, and subsequently synthesized as heteroepitaxial thin films. All magnetic MAX phases reported to date, in bulk or thin film form, are based on Cr and/or Mn, and they include (Cr,Mn)2AlC, (Cr,Mn)2GeC, (Cr,Mn)2GaC, (Mo,Mn)2GaC, and (V,Mn)3GaC2, Cr2AlC, Cr2GeC and Mn2GaC. A variety of magnetic properties have been found, such as ferromagnetic response well above room temperature and structural changes linked to magnetic anisotropy. In this paper, theoretical as well as experimental work performed on these materials to date is critically reviewed, in terms of methods used, results acquired, and conclusions drawn. Open questions concerning magnetic characteristics are discussed, and an outlook focused on new materials, superstructures, property tailoring and further synthesis and characterization is presented.

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Special quasirandom structures

Cited by 3,172 publications

References 17 publications

Feasibility of band gap engineering of pyrite FeS2

Feasibility of band gap engineering of pyrite FeS2

Vibrational thermodynamics: coupling of chemical order and size effects

Magnetic MAX phases from theory and experiments; a review

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