First-principles electronic structure calculations were performed for defect structure in non-stoichiometric CoAl and CoTi. In order to determine the type of constitutional defects, the compositional dependence curves both of formation energies and of lattice parameters were obtained by the calculations employing super-cells in various sizes. The defect formation energies were calculated with taking into account the compositional dependence of the chemical potential. The calculated results suggested that the Co vacancy was the dominant thermal-excitation defect even in the Co-rich side near the stoichiometry in CoTi.
First Principles Calculation of Defect Structure in Non-Stoichiometric CoAl and CoTi. M.Mizuno, H.Araki, Y.Shirai: Materials Transactions, 2005, 46[6], 1112-6
Table 1
Diffusivity of 57Co in CoAl
Al(at%) | Temperature(K) | D(m2/s) |
42 | 1630 | 1.48 x 10-14 |
42 | 1600 | 8.32 x 10-15 |
42 | 1570 | 4.49 x 10-15 |
42 | 1510 | 1.76 x 10-15 |
42 | 1476 | 2.80 x 10-16 |
42 | 1450 | 1.15 x 10-16 |
42 | 1380 | 5.91 x 10-17 |
42 | 1350 | 2.00 x 10-17 |
42 | 1317 | 1.42 x 10-17 |
42 | 1273 | 3.28 x 10-18 |
42 | 1250 | 2.30 x 10-18 |
46 | 1540 | 5.47 x 10-16 |
46 | 1510 | 3.95 x 10-16 |
46 | 1480 | 1.73 x 10-16 |
46 | 1430 | 9.43 x 10-17 |
46 | 1410 | 3.46 x 10-17 |
46 | 1380 | 1.33 x 10-17 |
50 | 1630 | 3.35 x 10-15 |
50 | 1600 | 2.16 x 10-15 |
50 | 1570 | 4.90 x 10-16 |
continued
Table 1 (continued)
Diffusivity of 57Co in CoAl
Al(at%) | Temperature(K) | D(m2/s) |
50 | 1540 | 3.26 x 10-16 |
50 | 1510 | 1.99 x 10-16 |
50 | 1480 | 7.80 x 10-17 |
50 | 1450 | 6.50 x 10-17 |
50 | 1380 | 8.20 x 10-18 |
50 | 1350 | 2.66 x 10-18 |
52 | 1600 | 7.19 x 10-16 |
52 | 1540 | 3.85 x 10-16 |
52 | 1480 | 6.64 x 10-17 |
52 | 1450 | 6.45 x 10-17 |