Revealing low-temperature atomic ordering in bulk Co-Pt with the high-throughput ab-initio method

Abstract

The low-temperature phase diagram of bulk Co-Pt is studied with a high-throughput ab-initio method. Global, hcp-, and fcc-restricted convex hulls are constructed to evaluate stable and metastable phases. It is found that fcc-L1 0 is energetically degenerate with hcp-B19. Both structures are unstable with respect to phase decomposition into hcp-D0 19 $fcc-b 2 at low temperature. Furthermore, L1 0 is an adaptive structure on the fcc-restricted convex hull which relates to the low energies of antiphase boundaries. Fcc-L1 2 is energetically degenerate with fcc-D0 23 for both Co 3 Pt and CoPt 3. L1 2-Co 3 Pt and L1 0-CoPt belong to the fcc-restricted convex hull. They might stabilize above the Co hcp/fcc transition and remain kinetically frozen below. L1 2-CoPt 3 is energetically well above the convex hull. Its experimental observation may result from yet unexplained finite-temperature effects. V

Tuning ofL10atomic order in Co-Pt nanoparticles:Ab initioinsights

“…The depletion initiates a considerable drop of L1 0 order at low temperatures because of the adaptive character of the L1 0 structure on the fcc-restricted convex hull. 87 However, it is shown that the L1 0 order can be considerably restored by tuning the total composition of small particles.…”

“…This is in accordance with the adaptiveness of L1 0 on the fcc-restricted convex hull. 87 The predicted appearance of low-temperature nonequiatomic secondary phases needs further experimental verification.…”

Study on lattice symmetry of sputtered Co–Cu–Pt metastable ordered thin films

“…The results reflect the structural improvement of the L1 1 films by the replacement of Co with Cu. Recently Chepulskii and Curtarolo analyzed the low-temperature structure in bulk Co-Pt using ab-initio method and concluded that CoPt binary alloy near equiatomic composition exhibited adaptive structures, a quasi-continuum of order structures (ground states) separated by finite energy gap at each composition [11]. The adaptive ground state has characteristics of low energies for antiphase boundary (APB) [12], which may let APBs and other planar defects to be thermodynamically acceptable, allowing the formation of long-period order structures at low temperatures.…”

Computational Materials Discovery Goes Platinum

“…In addition, the reader can prepare phase diagrams (as in Figs. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] linked to the appropriate structure URL locations. The Supplemental Material contains the whole set of geometrical and relaxed structures with ab initio total energies and formation enthalpies (see Ref.…”

“…Indeed, many recent studies present such calculations of PGM alloy structures . However, most of these studies consider a limited number of structures, at just a few stoichiometries of a single binary system or a few systems [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Some cluster expansion studies of specific binary systems include a larger set of structures, but limited to a single lattice type (usually fcc) [18][19][20][21][22][23].…”