First Principles Study of Structural Stability and Magnetic Property of Non-equilibrium Co-Mo Alloys

doi:10.1007/s40195-014-0120-9

Abstract

Abstract:

First principles calculations are carried out to investigate the structural stability of several non-equilibrium intermetallic phases in the cobalt (Co)-Mo system using spin polarized projected augmented-wave potentials. It is revealed that the Co₃Mo, CoMo, and CoMo₃ alloys are energetically favored to be in D0₁₉, B11, and A15 structures, respectively, and that the magnetic moments of Co atoms would decrease rapidly with an increasing percentage of Mo content and would most probably disappear when the content of Mo is no less than 50 at%. Generally, the calculated results in the present work match well with the available experimental observations.

Key words: First principles calculation, Transition metals, Cobalt, Magnetic property, Electronic structure

Li Shunning, Liu Baixin, Liu Jianbo. First Principles Study of Structural Stability and Magnetic Property of Non-equilibrium Co-Mo Alloys[J]. Acta Metallurgica Sinica (English Letters), 2014, 27(6): 1057-1062.

Figures/Tables 6

Fig. 1 The crystal structures discussed in the present work, calculations are carried out for A15, D03, D09, D019, and L12 structures at Co3Mo and CoMo3, and for B1, B2, B3, B81, and B11 structures at CoMo

Table 1 Calculated properties of Co3Mo, including lattice constants (a and c), atomic volume (V), total energy per atom (E), and magnetic moments per atom of Co and Mo (M Co and M Mo), in the A15, D03, D09, D019, and L12 structures arranged in the order of relative stability (from the most stable to the least stable)

Structures	a (nm)	c (nm)	V (10^-3nm³)	E (eV)	M _Co (μ_B)	M _Mo (μ_B)
D0₁₉	0.510	0.408	11.48	-8.113 (-8.108)	0.40	-0.20
L1₂	0.359		11.52	-8.606 (-8.058)	0.28	-0.13
A15	0.458		11.99	-7.950 (-7.882)	1.03	-0.28
D0₃	0.574		11.82	-7.840 (-7.823)	1.34	-0.07
D0₉			21.61	-5.970 (-5.941)	0.58	-0.17

Table 2 Calculated properties of CoMo, including lattice constants (a and c), atomic volume (V), total energy per atom (E), and magnetic moments per atom of Co and Mo (M Co and M Mo), in the B1, B2, B3, B81, and B11 structures arranged in the order of relative stability (from the most stable to the least stable)

Structures	a (nm)	c (nm)	V (10^-3nm³)	E (eV)	M _Co (μ_B)	M _Mo (μ_B)
B11	0.309	0.548	13.12	-8.878	0.00	0.00
B8₁	0.268	0.851	13.19	-8.778	0.55	-0.05
B2	0.297		13.15	-8.728	1.49	0.42
B1	0.485		14.24	-8.244	0.02	0.00
B3	0.525		18.09	-7.653	0.00	0.00

Table 3 Calculated properties of CoMo3, including lattice constants (a and c), atomic volume (V), total energy per atom (E), in the A15, L12, D03, D019, and D09 structures arranged in the order of relative stability (from the most stable to the least stable)

Structures	a (nm)	c (nm)	V (10^-3 nm³)	E (eV)
A15	0.486		14.37	-9.920
L1₂	0.386		14.35	-9.781
D0₃	0.614		14.46	-9.741
D0₁₉	0.554	0.435	14.45	-9.722
D0₉	0.445		22.00	-7.813

Table 4 Calculated elastic constants (C ij ) of the structures studied in the present work (in 105 MPa)

Phases	Structures	C ₁₁	C ₃₃	C ₄₄	C ₆₆	C ₁₂	C ₁₃
Co₃Mo	D0₁₉	4.72	5.01	1.39	1.10	1.95	1.70
	L1₂	3.99		1.75		2.02
	A15	3.95		-0.90		1.62
	D0₃	2.06		1.38		2.81
	D0₉	1.79		-0.11		0.23
CoMo	B11	2.97	4.09	1.19	0.85	2.88	1.87
	B8₁	3.18	4.08	0.25	0.69	2.68	1.69
	B2	1.36		0.57		3.20
	B1	3.18		-0.21		1.64
	B3	0.96		-0.98		1.58
CoMo₃	A15	4.73		0.85		1.63
	L1₂	2.73		1.05		2.55
	D0₃	2.98		0.89		2.48
	D0₁₉	3.24	3.46	0.55	0.19	2.15	2.20
	D0₉	2.42		-0.27		0.72

Fig. 2 Total density of states (DOS, states per eV per formula), partial DOS of the Co 3d (blue dash dot line), and Mo 4d (red short dash line) electrons of Co3Mo in the A15, D03, D09, D019, and L12 structures (the Fermi level is at the energy of zero)

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