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Newly synthesized double-perovskite superconductor (Ba0.54K0.46)4Bi4O12: A
DFT investigation
Poster · March 2020
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Newly synthesized double-perovskite superconductor (Ba0.54K0.46)4Bi4O12: A DFT investigation
Dept. of Materials Science and Engineering, Physics & EEE, University of Rajshahi, University of Yamanashi1,
Mirza H.K. Rubela, S.K. Mitrob, B.K. Mondalc, M.M. Rahamana, Md Saiduzzamana,e, J. Hossainc, A.K.M.A. Islamb,d*,, N. Kumadae
International Conference on Physics 5-7 March, 2020; Atomic Energy Centre Dhaka, Bangladesh
Abstract: The elastic, electronic, and thermodynamic properties of newly synthesized double-perovskite superconductor (Ba0.54K0.46)3Bi4O12 are studied by generalized gradient approximation (GGA) based
on density functional theory (DFT). Comparisons are made with two more recently discovered Bi-based double perovskite superconductors (Na0.25K0.45)Ba3Bi4O12 and (K1.0)(Ba1.0)3(Bi0.89Na0.11)4O12. Several
mechanical properties (e.g. independent elastic constants, mechanical stability, Young’s modulus, bulk modulus, shear modulus, Cauchy’s pressure, Poisson’s ratio, elastic anisotropy, and Peierls stress) are
calculated and analyzed. The electronic band structure, density of states, Fermi surface and total charge density distributions are evaluated. The thermodynamic properties such as Debye temperature, heat
capacities and volume thermal expansion coefficient at non-zero temperature and pressure are investigated by using quasi-harmonic model. Hybridization between Bi-6s and O-2p orbitals (dominant
contribution) is observed at EF similar to that seen in the previously published Bi-based perovskite superconductors. Both electron and hole like Fermi surfaces for (Ba0.54K0.46)4Bi4O12 double-perovskite are
observed which implies its multi-band nature. The flatness of the Fermi surface promotes transport features in Bi-based perovskite superconductors. The charge density distribution is basically spherical
around all the ions which essentially reveal the ionic characteristic of the material. The estimated electron–phonon coupling constant implies that the material is typically a strongly coupled superconductor.
*Corresponding author, e-mail: azi46@ru.ac.jp
Experimental & Theoretical Approach
Background and Introduction
(Ba0.54K0.46)4Bi4O12 (BKBO) double perovskite superconductor
Low-Temperature Hydrothermal synthesis and First-principles study
Teflon-lined
SPring-8 (SXRD for structure
Autoclave determination (λ = .41365 Å)
Starting materials molar ratios
KBiO3·H2O:Ba(OH)2·8H2O:KOH = 1:1:240
Single crystal of (Ba0.54K0.46)4Bi4O12 with Tc
~30 K
Structural optimization of (Ba0.54K0.46)4Bi4O12 double perovskite by CASTEP-code to explore
new physical properties : Experimental: a = 8.5207(2) Å; Theoretical a = 8.4175 Å with space
group Im-3m (#229).
Research Highlights
Investigation of numerous physical properties
of
newly
discovered
superconductor
(Ba0.54K0.46)4Bi4O12
Comparisons are made with two recently Bibased double perovskite superconductors
Band structure, DOS, features of Fermi
surface and distributions of charge density are
discussed.
Thermodynamic properties and electronA-site ordered AʹAʹʹ3B4O12 cubic
phonon coupling constant are analyzed.
double perovskite single crystal
Resistivity measurements
Density Functional Theory based CASTEPcode parameters (Virtual Crystal Structure
method); Debye model by GIBBS program
 Generalized Gradient Approximation
(GGA)- PBE
 Energy cut-off 900eV
 Monkhorst-Pack grid of 10×10×10
 Structural parameters
H2O = 12 ml
Standard four-terminal
Filtering Washing and Drying of
Ba0.54K0.46)4Bi4O12 crystal
mag
Cubic anvil high pressure cell
Hydrothermal reaction
180-260 ⁰C for 2 d
References: 1. Saiduzzaman et al. Inorg. Chem. 2019, 58, 11997-12001 2. A. K. M. A. Islam
et. al. Physica C 506 (2014) 53-58 3. Rubel et. al. Comput. Mater. Sci. 138 (2017) 160-165.
Results and Discussion
(Band structure and Density of States) Electronic properties of (Ba0.54K0.46)4Bi4O12 (Fermi surface and Electronic charge density)
Fig 1. Electronic band structure and (c) density of states of
(Ba0.54K0.46)4Bi4O12 double-perovskite superconductor. (b)
TDOS of (K1.0)(Ba1.0)3(Bi0.89Na0.11)4O12 [3] is shown in the
upper right panel for comparison.
Features of Band and DOS
Metallic characteristic with
large dispersion & significant
bands overlapping at (EF)
A potential hybridization
between Bi-6s and O-2p states
is seen at EF while minor for
Ba-4d and K-4s,3p orbitals
TDOS exhibits a value of 3.3
states/eV for the material
A similar TDOS shape of
(K1.0)(Ba1.0)3(Bi0.89Na0.11)4O12
superconductor
Bi-O bonds and atoms
contribute most in charge
distribution & spherical shape
responsible for ionic nature
Both electron-hole like EFsurface implies multi-band
nature.
Elastic and Thermodynamic properties of (Ba0.54K0.46)4Bi4O12
Fig 4. Fermi surface, and (b) 2D view and (c) 3D view of charge density map.
Table 1: Calculated lattice parameter a (Å), elastic constants Cij (GPa) bulk modulus B
(GPa), shear modulus G (GPa), Young’s modulus E (GPa), Pugh’s indicator (G/B),
machinability index (B/C44), Poisson’s ratio , elastic anisotropic factor A, Peierls stress
P (GPa), and Vickers hardness HV of (Ba0.54K0.46)4Bi4O12 superconductor.
Phase s
S1(cal.)
Expt.
S2(cal.)
Expt.
S3(cal.)
Expt.
a
C11
8.4175 283
8.5207
8.6277 223
8.5293
8.5067 241
8.5293
C12 C44
B
G
E
G/B
B/C44 A
55
37
131
59
154
0.45
3.54
p
Hv
0.46 1.9
5.5
48
53
107
65
162
0.61
2.02* 0.55 2.6
9.8*
64
49
123
63
161
0.51
2.51* 0.55 1.1
7.3*
S1: Ba0.54K0.46)4Bi4O12 S2: (Na0.25K0.45)Ba3Bi4O12 S3: (K1.0)(Ba1.0)3(Bi0.89Na0.11)4O12
. *Calculated by us.
Table 2: Calculated density  (g/cm3), longitudinal vl (km/s), transverse vt (km/s), average va
(km/s) elastic wave velocities, Debye temperature D (K) at zero pressure, and e-ph coupling
constant  of (Ba0.54K0.46)4Bi4O12 double-perovskite superconductor.
Superconductors
Fig 2. Pressure dependence of elastic
constants of (Ba0.54K0.46)4Bi4O12.
Analysis of Elastic and Thermal properties
Born stability criteria, brittle nature (hardness), elastic anisotropy (A),
high machinability index (M = B/C44) and moderate Peierls stress (p)
is observed for (Ba0.54K0.46)4Bi4O12.
Bulk modulus (B) is higher at low T; D falls quickly with rising T
and contribute to Cooper pairings; Heat capacities (Cp & Cv) and v
increases with increment of temperature (T).
(e-p) = 1.34 indicates nature of strongly coupled superconductor
Fig. 3. The temperature dependence of (a) bulk modulus, (b) Debye temperature, (c) specific heats
at constant pressure and (d) volume and (e) volume thermal expansion coefficient, VTEC of
(Ba0.54K
)4Bi4Ostats
View
publication
0.46
12 and data for (Na0.25K0.45)Ba3Bi4O12 [2] are shown for comparison.

l
t
a
D
 Ref.
(Ba0.54K0.46)4Bi4O12
7.818 5.78
2.746 3.068
395
1.34
This
(Na0.25K0.45)Ba3Bi4O12
7.660 5.059 2.931 3.253
382

2
(K1.0)(Ba1.0)3(Bi0.89Na0.11)4O12
7.539 5.240 2.891 3.222
385

3
Conclusions
Theoretical investigations on of (Ba0.54K0.46)4Bi4O12 are performed by CASTEP.
Metallic characteristics, strong hybridization between O-2p and Bi-6s orbitals and
ionic nature is evident from band structure, DOS and charge density map.
Fermi surface topology reveals the multi-band nature of the material.
Elastic constant (Cij) satisfy the Born stability criteria and ductile nature .
e-ph () parameter implies the behavior of a strongly coupled superconductor.
Various thermal properties are evaluated and analyzed for the first time.
Acknowledgements: This research work was partly supported by the Faculty of
Engineering, University of Rajshahi, Bangladesh (Grant number 26420678).