材料科學(xué)與工程外文翻譯--ruc高壓相變的第一性原理計(jì)算（英文）

1、See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/262994653First-principle calculations of high-pressurephase transformations in RuCARTICLE in EPL (EUROPHYSIC

2、S LETTERS) · JANUARY 2014Impact Factor: 2.1 · DOI: 10.1209/0295-5075/105/46004READS684 AUTHORS, INCLUDING:Jian HaoJiangsu Normal University31 PUBLICATIONS 191 CITATIONS SEE PROFILEYinwei LiJiangsu Normal Un

3、iversity47 PUBLICATIONS 401 CITATIONS SEE PROFILEAvailable from: Yinwei LiRetrieved on: 06 January 2016Jian Hao et al.Table 1: Calculated structural parameters of RuC within the ZB-type, WC-type and I 4mm structures

4、at selected pressures.P (GPa) Lattice parameters (? A) V0 Atomic coordinatesZB type 0 a = 4.602 (4.545(a),4.566(b)) 24.367 Ru 4a (0, 0, 0) C 4c (1/4, 1/4, 1/4) I 4mm 0 a = 2.854 21.818 Ru 2a (0, 0, 0) c = 5.356 C 2a (0,

5、0, 0.628) 10 a = 2.829 Ru 2a (0, 0, 0) c = 5.279 C 2a (0, 0, 0.626) WC type 0 a = 2.963 (2.908(c),2.921(a)) 20.531 Ru 1a (0, 0, 0) c = 2.701 (2.822(c),2.672(a)) C 1f (2/3, 1/3, 1/2) 30 a = 2.875 c = 2.652(a)Reference [8]

6、. (b)Reference [9]. (c)Reference [6].plane-wave kinetic energy cutoff of 520 eV. Monkhorst- Pack Brillouin zone sampling grids with the resolutionof 2π × 0.03 ? A ?1were used, resulting in total energy con- vergence

7、 to better than 1 meV/atom. Elastic constants were calculated by the strain-stress method [14] with gridsdenser than 2π × 0.02 ? A ?1. The phonon dispersion curves were computed using the phonopy program [15], which

8、 is an open source package of phonon calculations based on the supercell approach [16]. This approach uses the forces obtained by the Hellmann-Feynman theorem calculated from the optimized supercell through the VASP code

9、. We used 3 × 3 × 3 supercells (27 RuC formula units) for all the three phases.Results and discussion. – After full geometry opti- mizations, the ZB-type and WC-type structures keep their initial symmetries, as

10、 shown in fig. 1. In the ZB-type structure, each Ru (C) atom is bonded with four C (Ru) atoms with Ru-C bond length of 1.98 ? A at ambient pres- sure. For the WC-type structure, each Ru (C) atom is surrounded by six C (R

11、u) atoms with relative longer Ru-C bond length of 2.179 ? A at ambient pressure. In table 1 the structural parameters of the ZB-type and WC-type phases are compared with the available experimental data [6] and earlier th

12、eoretical results [8,9]. A good agreement within a 2% interval is found. The cell parameters and atomic positions for Pmn21- RuC were also fully optimized at selected pressures. How- ever, we surprisingly found that the

13、symmetry of Pmn21 changes during the optimization. In the Pmn21 structure of OsC [10], each Os atom is coordinated by five C atoms, forming distorted OsC5 pyramids. In each OsC5 pyra- mid, the four bottom Os-C bonds can

14、be classified into two types with slightly different bond lengths, as shown in fig. 1(c). Once the Os is replaced by Ru, the four bottom Ru-C bonds automatically become equal during optimization at all pressures studied.

15、 Consequently, stan- dard RuC5 pyramid (Ru-C bond lengths of 1.984 ? A andFig. 1: (Color online) Crystal structures of RuC in (a) ZB- type, (b) WC-type and (d) I 4mm structures. (c) is the Pmn21 structure of OsC to show

16、the structure change from Pmn21 to I 4mm. Big black and small blue spheres represent Ru (Os) and C atoms, respectively.2.113 ? A × 4) is formed and the Pmn21 structure trans- forms to a higher symmetric tetragonal s

17、tructure with space group I 4mm (fig. 1(d)).Figure 2(a) presents the calculated enthalpies of the ZB-type and WC-type structures with respect to the I 4mm structure. One observes obviously that the I 4mm structure become

18、s energetically more favorable than the ZB type above 9.3 GPa. The I 4mm structure is stable up to 26 GPa, above which the WC-type structure takes over. According to our enthalpy results, a phase sequence of ZB type → I4