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Journal of Physics and Chemistry of Solids
journal homepage: www.elsevier.com/locate/jpcs
Theoretical study the electronic, elastic properties and thermodynamics
properties of ternary phosphide SrPt
6
P
2
Wenyan Tian
a,
⁎
, Jianghui Cai
b
, Haichuan Chen
c
a
College of Electronics and Information Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, China
b
College of Computer Science and Technology, Taiyuan University of Science and Technology, Taiyuan 030024, China
c
College of Electrical Engineering and Information Technology, Xihua University, Chengdu 610039, China
ARTICLE INFO
Keywords:
First-principles
Mechanical properties
Quasi-harmonic Debye model
Thermodynamic properties
Superconductor
ABSTRACT
The structural, electronic, elastic properties of superconductivity SrPt
6
P
2
have been investigated and analyzed
using generalized gradient approximation within the density functional theory. The optimized lattice constant is
in well agreement with the experimental data. The total density of states (DOS) results demonstrates that
SrPt
6
P
2
is metallic in character, and the Fermi level is mainly the contribution of 5d orbitals of Pt and with small
contributions from P-p and Sr-d states. The elastic constants, bulk modulus, Young's modulus and shear
modulus are also successfully obtained. The calculated elastic constants meet the mechanical stability criteria.
The B/G ratio, Poission's ratio and Cauchy pressure indicated that it possesses ductile. The Vickers hardness is
7.49 GPa, suggesting that it is a soft material. Though the quasi-harmonic Debye model, the thermodynamics
properties of SrPt
6
P
2
have been obtained. The results show the
C
v
,
C
p
and
is about 863.5 J/mol K, 895.6 J/
mol K and 4.0
5
×10
5
K
−1
at 0 GPa and 300 K, respectively. The Debye temperature is 273.7 K, melting
temperature is 2271 ± 300 K and the minimum thermal conductivities
min
is 0.495 W m
−1
K
−1
. It has also
been shown that the
C
v
,
C
p
and
decrease with increasing pressure at given temperature while increase with
increasing temperature at given pressure. Finally, the superconducting parameters are evaluated by the
McMillan equation.
1. Introduction
The discovery of ternary alkali metal and transition metal super-
conductors has recently revitalized interest in intermetallic super-
conductivity [1–3]. The discovery of new superconductors has gener-
ated great impact in the condensed matter physics field [4–6].
Recently, Lv et al. [7] have reported superconductivity at ~0.6 K in a
metal-rich ternary phosphide SrPt
6
P
2
. According to their reported, the
new ternary phase with a cubic structure in which the Sr atoms located
a face-centered-cubic (fcc) and each vertex of cube positions, the P and
Pt atoms displaying a unique three dimensional network of vertex-
shared Pt
6
P nominal trigonal prisms. However, except for the observa-
tion of superconductivity and determination of the crystal structures,
other data in the literature are still very limited. The purposes of the
present investigation are to calculate the electronic, elastic and
thermodynamic properties of this new ternary phosphide SrPt
6
P
2
.
2. Calculation methods
All of the first-principles calculations reported in this work were
carried out by using the ultra-soft pseudopotential plane-wave method
based on the density functional theory (DFT) [8]. The exchange-
correlation potential was described within the generalized gradient
approximation as parametrized by Perdew, Burke and Ernzerhof
(GGA-PBE) [9]. The 4s
2
4p
6
5s
2
for Sr, 5d
9
6s
1
for Pt and 3s
2
3p
3
for P
electron states were treated as valence electrons. For the structural
optimization and energy band calculations, the first Brillouin zone
integrations are performed using Monkhorst-Pack k-point meshes. A
plane-wave cutoff energy of 550 eV and 10×10×10 k-point meshes
were chosen to be sufficient to reduce the total energy to less than
2 meV per atom.
3. Results and discussions
3.1. Structure and electronic properties
SrPt
6
P
2
crystallizes in a cubic structure with the space group
Pa3
(No. 205) and has four formula units per conventional cell (Fig. 1).
Here, the Sr atoms located at the 4a Wyckoff positions corresponding
to a face-centered-cubic (fcc) lattice, P atoms at 8c Wyckoff positions,
http://dx.doi.org/10.1016/j.jpcs.2017.03.002
Received 28 October 2016; Received in revised form 6 January 2017; Accepted 2 March 2017
⁎
Corresponding author.
E-mail address: wytiantust@163.com (W. Tian).
Journal of Physics and Chemistry of Solids 106 (2017) 10–15
Available online 02 March 2017
0022-3697/ © 2017 Elsevier Ltd. All rights reserved.
MARK