EXPLORING THE ELECTRONIC, MAGNETIC, OPTICAL AND THERMOELECTRIC PROPERTIES OF Mn3Si2Te6 BY USING THE STRAIN EFFECT: A DFT STUDY

The study investigates the structural, magnetic, electronic, optical and thermoelectric properties of MST (half-semi metallic) compound under strain engineering. Experimentally, MST is metallic nature with zero gap, low thermal conductivity, and minute thermoelectric efficiency (ZT 0.01 at 300K). By applying biaxial strain (tensile and compressive), the gap increased, showing a shift from -4% to +15% with SCF and -3% to +10% with GGA and GGA + TB-mBJ methods. At 4% tensile strain, MST exhibited half-semi metallic behavior with a significant gap (1.24 eV) at a high-symmetry point. Hybrid + SOC calculations showed enhanced thermoelectric performance, with ZT reaching 0.716 for p-type and 0.723 for n-type, suggesting MST potential for thermoelectric applications.

1. 1
Start with the name of Allah who is the Start with the name of Allah who is the
most meriful and beneficent.most meriful and beneficent.

2. Exploring The Electronic, Magnetic, Optical and Thermoelectric Exploring The Electronic, Magnetic, Optical and Thermoelectric
Properties of MnProperties of Mn
33
SiSi
22
TeTe
66
using the Strain Effect: A DFT Study. using the Strain Effect: A DFT Study.
Presenter: Mazhar Haleem
M.Phil Scholar in Physics
Roll No. # 9317
Supervisor: Dr. Yasir Saeed (AUST)
Co-Supervisor: Dr. Muhammad Shafiq (AUST)
Department of Physics

3. 3
OutlineOutline

Thermoelectric Effect and Its SignificanceThermoelectric Effect and Its Significance

IntroductionIntroduction

MotivationsMotivations

Aim and ObjectiveAim and Objective

Research MethodologyResearch Methodology

Result and DiscussionResult and Discussion

ConclusionsConclusions

Future PlansFuture Plans

4. 4
THERMOELECTRIC (TE) EFFECTTHERMOELECTRIC (TE) EFFECT
““Is the direct conversion of heat into electricity or vice versa.”Is the direct conversion of heat into electricity or vice versa.”

SEEBECK EFFECT: Temp difference, emf is produced at the junction of two different metals.
Ref: Ceram, 24, 213--223 (2021).
TE effect is based on seebeck and peltier effect:TE effect is based on seebeck and peltier effect:

5. 5
THERMOELECTRIC (TE) EFFECTTHERMOELECTRIC (TE) EFFECT
““Is the direction conversion of heat into electricity or vice versa.”Is the direction conversion of heat into electricity or vice versa.”
TE effect is based on seebeck and peltier effect:TE effect is based on seebeck and peltier effect:
PELTIER EFFECT: Opposite to seebeck, due to potential difference heat is produced at
different junction (either absorb or evolved)
Ref: Ceram, 24, 213--223 (2021).

6. 6
Significance of a TE Material’s:Significance of a TE Material’s:

FIGURE OF MERIT:

The good thermoelectric materials should possess:
1. Large Seebeck coefficients ‘S’ and High electrical
conductivity σ (Directly Proportional to ZT).
2. Low thermal conductivity K (In-directly Propertional to
ZT).
3. K = K
e
+ K
ph

The example for Thermoelectric materials
1. Bismuth Telluride (Bi
2
Te
3
) with ZT = 0.6 at T = 400,
2. Lead Telluride (PbTe) with ZT = 0.8 at T = 773,
3. Silicon Germanium (Si
1-x
Ge
x
) with ZT = 0.9 at T =
1023,
Ref: Y. Saeed, "Tuning the Transport Properties of Layered Materials for Thermoelectric
Applications using First-Principles Calculations." 1-108 (2014).
ZT=
S
2.
σ
κ
T

7. Introduction
•From theoretical and experimental results show that graphene
has strong vander waals interaction between the layer
(a)
.
•Mn
3
Si
2
Te
6
(MST)

shows metallic nature due to strong vander
waals forces like graphite structure and extra Mn
2
between the
Layer
(b)
.
•The vdW distance of MST is 2.38 Å, smaller than graphite vdW
distance 3.4 Å

7 Ref(b): Phys. Rev. B, 103, 245122-245122 (2021) (b)
Ref(a): Nano Lett. 15, 319-325 (2015) (a)

8. 8

Firstly, convert metal to semi-conductor by applying strain
engineering.

Experimentallly Analysis, In Fig. 1 at 300 K temp, the
seebeck coef. decrease with 0.5 mV/K or 0.0005 μV/K.

The Figure of merit ZT relatively small value ~ 0.010, at
Temp 300 K.

My interest of research, to enhance the thermoelectric
properties of Mn
3
Si
2
Te
6
by applying Strain (compressional
and tensile).

Finding the Seebeck cofficient ‘S’, electrical conductivity σ,
thermal conductivity K
e
, Figure of merit zT and Thermo-
power under strain.
Motivations:Motivations:
Ref: Phys. Rev. B, 103, 245122-245122 (2021)
Fig. 1
Fig. 2

9. 9

In Recently DFT studies, the
Cr
2
Si
2
Te
6
show semi-conductor
nature in spin (up/dn).

The bandgap, spin up is 0.57 eV
and spin dn is 0.65 eV, respectively.

The formula for Cr
2
Si
2
Te
6
is similar
to Mn
3
Si
2
Te
6
compound.
Motivations:Motivations:
Ref: J. Mater. Chem. C, 4, 315–322, (2016)

10. 10

1
st
, To determined the structural, electronic, magnetic and
optical properties of pristine material Mn
3
Si
2
Te
6
.

2
nd
, To determined the structural, electronic, magnetic and
optical properties of strain Mn
3
Si
2
Te
6
.

3
rd
, To determine the Thermo-electric (TE) of pristine and
strain Mn
3
Si
2
Te
6.

Aim and Objectives:Aim and Objectives:

11. 11

The calculation were carried out by
using the WIEN2k package, which is
based on DFT Study.

We performed scf calculation to
compared with experimental result.

The Exchange-correlation potential, Wu-
Cohen is used only for providing suitable
bandgap as compared to other potential.

BoltzTrap package use for
thermoelectric properties.
Research Methodology:Research Methodology:

12. Results and Discussion:
12

13. Structural Properties:
13
Structural Properties:

14. Structural Properties of MnStructural Properties of Mn
33
SiSi
22
TeTe
66
compound: compound:
Fig. 1 Top view of Mn
3
Si
2
Te
6
. Fig. 2 Side view of Mn
3
Si
2
Te
6
.

15. Volume Optimization:
15

16. •Hexagonal structure of Mn
3
Si
2
Te
6
with space
group P3¯1c.
•In expermental the parameters are:
a = b = 7.0346 Å, c = 14.2435 Å, c/a ratio = 2.025.
•After optimization the parameters are:
a = b = 7.0863 Å, c = 14.0366 Å, c/a ratio = 1.981.

16
Ref: Phys. Rev. B, 103, 245122-245122 (2021)
Before and after volume optimize the lattice parameter are:
Bulk Mn
3
Si
2
Te
6
material.

17. Volume Optimization Curve of MST material:


18. Electronic Properties: Band, Dos without strain
18

19. 19
Electronic Properties of pristine material Mn
3
Si
2
Te
6
.

20. TDOS of pristine material MST:

21. PDOS of ‘Mn’ Atom, with orbital contribution:

22. PDOS of ‘Si’ Atom, with orbital contribution:

23. PDOS of ‘Te’ Atom, with orbital contribution:

24. 24
Electronic Properties under strain:
Tensile (+) and compressive (-) strain for Bulk Mn
3
Si
2
Te
6

24

25. 25
Tensile Strain from 0 to 4% (Metallic) of MST:Tensile Strain from 0 to 4% (Metallic) of MST:

26. 26
Tensile Strain from 5 to 15% (Semi-metal) of MST:Tensile Strain from 5 to 15% (Semi-metal) of MST:

27. 27
Convert 0% (Metal) to 5% (Semi-metal) of MST:Convert 0% (Metal) to 5% (Semi-metal) of MST:

28. 28
Compressive Strain from 0 to 4% (metallic) of MnCompressive Strain from 0 to 4% (metallic) of Mn
33
SiSi
22
TeTe
66
::

29. Biaxial Strain apply in Hexagonal Mn
3
Si
2
Te
6
:

30. 30
Optical Properties:

30

31. Absorption Coef. of Mn
3
Si
2
Te
6
:

32. 32
Thermal Properties:

32

33. Seebeck coefficient with 5% strain of MST:

34. Table for 5% strain with Seebeck coefficient:
With
Strain
MST
Temperature
Scale
(Kelvin)
Seebeck
(μV/K)
p-type
Seebeck
(μV/K)
n-type
5% 300 901 879
5% 400 693 660
5% 500 573 536
5% 600 485 447
5% 700 427 385
5% 800 375 343

35. Power Factor with 5% strain of MST:

36. Table for 5% strain with Power Factor:
With
Strain
MST
Temperature
Scale
(Kelvin)
PF
(W/mK
2
s)
p-type
PF
(W/mK
2
s)
n-type
5% 300 26.53 x 10
10
16.88 x 10
10
5% 400 24.05 x 10
10
14.70 x 10
10
5% 500 21.17 x 10
10
12.29 x 10
10
5% 600 17.76 x 10
10
9.82 x 10
10
5% 700 13.70 x 10
10
7.47 x 10
10
5% 800 9.35 x 10
10
5.05 x 10
10

37. Figure of merit ZT with 5% strain MST:

MST ZT value is ~ 0.98, 0.96 (p-type, n-type) at 300 K larger then the experimental value
of (0.01). Bi
2
Te
3
(ZT = 0.6 at T = 400K), and PbTe (ZT = 0.8 at T = 773 K).
Ref: Y. Saeed, "Tuning the Transport Properties of Layered Materials for Thermoelectric
Applications using First-Principles Calculations." 1-108 (2014).

38. Table for 5% strain with Figure of Merit ZT:
With
Strain
MST
Temperature
Scale
(Kelvin)
ZT

p-type
ZT

n-type
5% 300 0.98 0.96
5% 400 0.95 0.93
5% 500 0.92 0.89
5% 600 0.89 0.85
5% 700 0.87 0.81
5% 800 0.84 0.76

39. Conclusions:

Calculated band structure of MST without strain shows metallic behavior.

We apply upto 4% compressive strain and upto 15% tensile strain.

The results show the metallic character of MST upto 4% compressive strain
and upto 4% tensile strain.

On applying 5% tensile strain MST show bandgap of 0.732 eV, which
decrease on applying further tensile strain.

We calculate the absorbtion coef. of MST without and 5% tensile strain.

We calculate the thermoelectric properties such as seebeck coef. , optical
conduc, thermal cond, power and zt of mst at 5% tensile strain from 300 to
800 k.

Our calculated ZT value is ~ 0.98 at 300 K which is larger then the
experimental value of unstrain MST (0.01), and comparable to the well-
known TE material, Bi
2
Te
3
(ZT = 0.6 at T = 400K), and PbTe (ZT = 0.8 at T =
773 K).


39

40. Conclusions:

Calculated band structure of MST without strain shows metallic behavior.


40

41. Conclusions:

We apply upto 4% compressive strain and upto 15% tensile strain.
41

42. Conclusions:

The results show the metallic character of MST upto 4% compressive strain.
42

43. Conclusions:

The results show the metallic character of MST upto 4% tensile strain.
43

44. Conclusions:

On applying 5% tensile strain MST show bandgap of 0.732 eV, which
decrease on applying further tensile strain.


44

45. Conclusions:

We calculate the absorbtion coef. of MST without and 5% tensile strain.
45

46. Conclusions:

We calculate the thermoelectric properties such as seebeck coef. , power
factor and ZT of MST at 5% tensile strain from 300 to 800 k.


46

47. Conclusions:

Our calculated ZT value is ~ 0.98 at 300 K which is larger then the
experimental value of unstrain MST (0.01), and comparable to the well-
known TE material, Bi
2
Te
3
(ZT = 0.6 at T = 400K), and PbTe (ZT = 0.8 at T =
773 K).


47

48. 48
Future Plan:

49. 49

50. 50
Figure of merit ZT with 0% without strain MST: