View
9
Download
0
Category
Preview:
Citation preview
Chemical bonding
Partial Density Of States (PDOS)
Charge density distribution
Charge transfer plot
Energy projected charge density
Electron Localization Function (ELF)
Crystal Orbital Hamilton Population analysis (COHP)
Mulliken population analysis
Born effective charge analysis
Bader topological analysis
Bonding Character in Materials
Ionic
Covalent
Metallic
The different types of bonding is strongly dependent on the electronic structure.
Electron Localization Function (ELF)
ELF becomes 1 either for
– perfect covalent bond
- lone paired electron
In homogenious electron gas the ELF is 0.5
- metallic bond
Charge transfer plot
∆ρ(r) = ρ(r) comp. - ρ(r)o.f.a
NaCl
Na Cl
In pure ionic solids,
electrons are completely
transferred from electro-positive
atom to electronegative atom.
Ionic bonding
Charge difference ELF
C in diamond structure
As opposed to ionic bonding in
which a complete transfer of
electrons occurs, covalent
bonding occurs when two (or
more) elements share their
electrons.
Charge density Charge difference ELF
Covalent bonding
Na
The valence electrons are
homogeneously distributed in the
space in between the atoms.
Charge density Charge difference ELF
Metallic bonding
LiH Li H
Ionic hydrides
Charge density Charge difference ELF
B2H6
B
H
Covalent Hydrides
Charge density Ch. diff. ELF
ScH2
Sc
H
Metallic Hydrides
Density Of States
Bonding nature in complex hydrides
Ex. LiAlH4
Li3AlH6
Interaction between Li - [AlH4] ionic
Interaction between Al – H within [AlH4]
covalent
ionic Li+Al3+ H4–
?
LiAlH4
Pure Ionic - A. Aguayo, D.J. Singh, Phys. Rev. B 69 155103 (2004)
−10 −7.5 −5 −2.5 0 2.5 5 7.5 10
1
2
3
4
0.1
0.2
0.2
0.4
0.6
0.8
0.1
0.2
0.3H
Al
Li
Total
EF
Energy (eV)
DO
S (
sta
tes
eV−
1)Non-metal
Energitically degenerated
Al – s and H – s states
Possible covalent type of interaction ?
DOS for Li3AlH6; s- states are shaded
DOS for Li3AlH6
ELF
0.50
0.75
0.100.20
0.05
0.01 -0.10
(a) (b) (c)
0.01 0.15
0.10 0.0
-0.01 0.25
1.0
0.001
H
Al Al
H
Al
H HLiLi
H
LiH
Charge density Charge transfer
Chemical bonding in Li3AlH6
−10 −7.5 −5 −2.5 0 2.5 5 7.5 10
1
2
3
4
0.1
0.2
0.2
0.4
0.6
0.8
0.1
0.2
0.3H
Al
Li
Total
EF
Energy (eV)
DO
S (
state
s eV
−1)
Energy projected (-7.5 to -6 eV) charge
density plot in Li3AlH6
Al-H 0.107
Li-H -0.014
2.000
10.968
1.844
Li
Al
H
Li3AlH
6
Al-H 0.173
Li-H -0.015
2.000
11.001
1.738
Li
Al
H
LiAlH4
Al-H 0.091 10.782
1.739
Al
H
AlH3
Be-H 0.045 2.366
1.822
Be
H
BeH2
Mg-H -0.04010.135
1.933
Mg
H
MgH2
C-H 0.384 6.256
0.936
C
H
CH4
Li-H -0.0082.014
1.986
Li
H
LiH
OVPOP(AB) M.CHARGEATOMSystem
Mulliken population analysis for selected hydrogen content compounds
0.1250.1160.1530.2100.125-0.088-0.817-0.831-0.911Z(H2)
0.0270.073-0.190-0.1740.0270.082-0.846-0.738-1.018Z(H1)
-0.0010.000-0.0010.000-0.0010.0341.7352.2372.237Z(Al)
0.1020.0240.0610.0140.1020.0170.9850.9570.99Z(Li)
yxzyxzzxyzxyzzyyxx
Calculated-Born-effective-charge tensor elements
(Z*) for the constituents of Li3AlH6
Chemical Bonding in Li3AlH6
- interaction between Li and [AlH4]- is ionic.
- bonding charecter of Al and H within [AlH4]- is a mixure of
ionic and covalent.
Bonding interaction in complex hydrides are not simple ionic or covalent
character but the mixture of them.
Recommended