Supplemental material for “Electrical/thermal transport and electronic structure of the
binary cobalt pnictides CoPn2 (Pn = As and Sb)”
Yosuke Goto, Syuhei Miyao, Yoichi Kamihara, and Masanori Matoba
Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology, Keio
University, Yokohama 223-8522, Japan
Synthesis of polycrystalline CoPn (Pn = P, As, and Sb)
Polycrystalline CoPn (Pn = P, As, and Sb) was synthesized by the solid-state reaction of Co (Sigma
Aldrich, 99.995%), P (Kojundo Chemical, 99.9999%), As (Kojundo Chemical, 99.9999%), and Sb
(Kojundo Chemical, 99.9%). Stoichiometric ratios of starting materials were mixed and pelletized in
Ar-filled glove box (MIWA Mfg; O2, H2O < 1 ppm). The pellet was heated in a sealed silica tube at
400 C for 20 h. Then, the sample was heated to 900 C with 30 Ch1 and maintained at this
temperature for 30 h, followed by furnace cooling. Relative density of samples was calculated at 54%,
66%, and 75% for CoP, CoAs, and CoSb, respectively.
Density functional theory calculation of CoPn
The electronic structure calculation was performed using the plane-wave projector augmented-wave
(PAW)1,2 method implemented in the Vienna ab initio Simulation Package (VASP) code.3,4 The
exchange-correlation potential was approximated using the generalized gradient approximation by the
Perdew–Becke–Ernzerhof (PBE) method.5 A cutoff of 600 eV was chosen for the plane-wave basis set.
The Brillouin zone was sampled by a 24 × 40 × 24, 24 × 40 × 24, and 32 × 32 × 24 Monkhorst–Pack
grid6 for CoP, CoAs, and CoSb, respectively.
REFERENCES
1
2
3
4
5
6
P. E. Blöchl, Phys. Rev. B 50, 17953 (1994).
G. Kresse and D. Joubert, Phys. Rev. B 59, 1758 (1999).
G. Kresse and J. Furthmüller, Comput. Mater. Sci. 6, 15 (1996).
G. Kresse and J. Furthmüller, Phys. Rev. B 54, 11169 (1996).
J. P. Perdew, K. Burke, and M. Emzerhof, Phys. Rev. Lett. 77, 3865 (1996).
H. J. Monkhorst and J. D. Pack, Phys. Rev. B 13, 5188 (1976).
FIGURE CAPTIONS
FIG. S1.
X-ray diffraction patterns of CoPn (Pn = P, As, and Sb). Vertical marks at the bottom indicate the
calculated Bragg diffraction angles of CoPn. The asterisk represents the diffraction due to unknown
impurity phase.
FIG. S2.
(a) Electrical resistivity () and (b) Seebeck coefficent (S) as functions of temperature (T) of CoPn (Pn
= P, As, and Sb).
FIG. S3.
(a) Thermal conductivity () and (b) dimensionless figure of merit (ZT) as functions of temperature (T)
of CoPn (Pn = P, As, and Sb).
FIG. S4.
Theoretical density of states (DOS) of CoPn (Pn = P, As, and Sb). The Fermi energy is set to 0 eV.
FIG. S5.
(a) Total thermal conductivity (tot), (b) electronic thermal conductivity (el), and (c) lattice thermal
conductivity (l) as a function of temperature (T) of CoPn2 (Pn = As and Sb). The el was calculated
using WiedemannFranz relation, el = LT1, where L is the Lorenz number, L = 2.45  108 WK2.
The l was calculated by subtracting the el from .
FIG. S6.
Absorption spectra () of CoPn2 (Pn = As and Sb) converted from reflectivity spectra using
KubelkaMunk relation. The direct-type absorption edge was estimated by the onset of the
(h/s)2–h plot.
TABLE CAPTION
TABLE SI.
Calculated lattice parameters of CoPn (Pn = P, As, and Sb). CoP and CoAs belongs to orthorhombic
space group Pnma (MnP-type) and CoSb belongs to hexagonal space group P63/mmc (NiAs-type).
The values in parentheses are the statistical errors. Other errors such as temperature fluctuations (< 1
K) should be considered.
CoP
Diffraction intensity (kcounts)
20
0
CoAs
20
0
*
CoSb
20
0
10
FIG. S1
20
30
40
2 (deg.)
50
60
70
0
(a)
10
(m cm)
CoAs
-1
10
CoSb
-2
10
CoP
-3
10
1
S (V K )
0
-20
CoSb
CoP
(b)
CoAs
-40
0
300
600
T (K)
FIG. S2
900
15
CoSb
10
CoAs


 (W m K )
(a)
5
CoP
0
0.02
(b)
CoAs
ZT
CoP
0.01
CoSb
0.00
0
300
600
T (K)
FIG. S3
900
CoP
total
Co 3d
P 3p
DOS (states/eV)
20
0
CoAs
total
20 Co 3d
As 4p
0
CoSb
20
0
-5
FIG. S4
total
Co 3d
Sb 5p
0
Energy (eV)
5
tot (Wm-1K-1)
CoAs2
10
CoSb2
5
0 (a)
el (Wm-1K-1)
(b)
10
5
CoSb2
CoAs2
0
l (Wm-1K-1)
CoAs2
10
5
CoSb2
0 (c)
300
FIG. S5
400
500
600
T (K)
700
800
900
-1 2
2
(hs ) (eV )
4 CoAs
2
0
CoSb2
20
0
0
FIG. S6
1
2
3
Photon energy (eV)
4
Table SI
CoP
CoAs
CoSb
a (nm)
b (nm)
c (nm)
0.50781(1)
0.52827(1)
0.388508(9)
0.328102(7)
0.348855(8)
--
0.55887(2)
0.58688(3)
0.51899(2)