The investigation Thermal Stability of optical properties of metallic Paints under different temperatures

Abstract

v

ABSTRACT

In this thesis, electronic structure calculations for some selected double perovskite oxides have

been done, using two electronic structure codes,

via Mindlab and WIEN2k. The selected compounds are

Sr

2

CrZrO

6

, Sr

2

MnNbO

6

, Sr

2

FeMoO

6

and Sr

2

NiRuO

6

.

A systematic study

was

carried out adopting

dif

ferent approximation methods viz

, LMTO

-

ASA and LMTO

-

P

LW for the cubic structure,

FP

-

LAP

W

method for pseudo cubic and tetragonal crystalline structures. The calculation of the density of the states

(DOS)

was

performed in terms of the local spin density approximation and Hubbard potential (LSDA+U),

including the spin

-

orbit coupling.

In the LM

TO

-

ASA and LMTO

-

PLW approximation methods, the DOS of Sr

2

FeMoO

6

was

obtained and found to agree very well with published reports.

Half metallic character through the spin

down channel and the ferrimagnetic ordering were observed with notable hybridization

among the 3d, 4d

and

Oxygen within Fermi level. A

ll methods used here, show that, the half

-

metallic character through

different bands and channels was seen in all compounds except Sr

2

NiRuO

6

compound, which shows

normal metallic conduction in LMTO

-

ASA and L

MTO

-

PLW methods. For the two methods, the obtained

values of the magnetic moments indicate that, the

Sr

2

CrZrO

6

is frustrated system, while the

Sr

2

MnNbO

6

compound has

a ferrimagnetic ordering

v

ABSTRACT

In this thesis, electronic structure calculations for some selected double perovskite oxides have

been done, using two electronic structure codes,

via Mindlab and WIEN2k. The selected compounds are

Sr

2

CrZrO

6

, Sr

2

MnNbO

6

, Sr

2

FeMoO

6

and Sr

2

NiRuO

6

.

A systematic study

was

carried out adopting

dif

ferent approximation methods viz

, LMTO

-

ASA and LMTO

-

P

LW for the cubic structure,

FP

-

LAP

W

method for pseudo cubic and tetragonal crystalline structures. The calculation of the density of the states

(DOS)

was

performed in terms of the local spin density approximation and Hubbard potential (LSDA+U),

including the spin

-

orbit coupling.

In the LM

TO

-

ASA and LMTO

-

PLW approximation methods, the DOS of Sr

2

FeMoO

6

was

obtained and found to agree very well with published reports.

Half metallic character through the spin

down channel and the ferrimagnetic ordering were observed with notable hybridization

among the 3d, 4d

and

Oxygen within Fermi level. A

ll methods used here, show that, the half

-

metallic character through

different bands and channels was seen in all compounds except Sr

2

NiRuO

6

compound, which shows

normal metallic conduction in LMTO

-

ASA and L

MTO

-

PLW methods. For the two methods, the obtained

values of the magnetic moments indicate that, the

Sr

2

CrZrO

6

is frustrated system, while the

Sr

2

MnNbO

6

compound has

a ferrimagnetic ordering.

The results for the pseudo cubic and tetragonal structures show

that there is hybridization among

the 3d and 4d

states

in the spin

-

up channels where as a gap is found in the spin

-

down channels in both

Sr

2

MnNbO

6

and Sr

2

NiRuO

6

.

T

he conduction band is seen in the spin

-

up and spin

-

down channels in

Sr

2

CrZrO

6

and Sr

2

FeMoO

6

respectively. The resulting magnetic moments indicate that all the pseudo

cubic and tetragonal structures are having ferromagnetic ordering except the Sr

2

FeMoO

6

having a

ferrimagnetic ordering. The values of the spin magnetic moments of the 3d elements ar

e in the range of

1.737 μ

B

to 3.949 μ

B

for pseudo cubic and 1.710 μ

B

to 3.971 μ

B

for tetragonal structure. The values of the

spin magnetic moments of the 4d elements are in the range

of

0.013 μ

B

to 1.058 μ

B

and 0.001 μ

B

to 1.225

μ

B

for pseudo cubic and te

tragonal structures respectively. The values of the orbital magnetic moments of

the 3d elements are in the range of 0.004 μ

B

to 0.20 μ

B

and 0.0044 μ

B

to 0.22 μ

B

for the two structures

respectively. For the 4d elements

,

the

range

of

0.002 μ

B

to 0.10 μ

B

and

0.0001μ

B

to 0.1 μ

B

for the two

structures respectively. These values indicate that the effect of the orbital magnetic moment vary from

quenched to weakly unquenched to unquenched as going from Zr to Nb to Ru. A similar trend is observed

in the 3d orbitals

as going from Cr to Mn to Ni. For the Sr (5s) and O(2p) orbital, the orbital moments are

negligibly small.

The Sr

2

NiRuO

6

shows ferromagneti

c

ordering

in

accordance with the super exchange

interaction

푒

푔

2

−

푂

−

푒

푔

0

of Goodenough

-

Kanamori

-

Anderson (GKA).