gested a phase transition for nanocrystals of smaller size, whereby the valency of
Mn changes from Mn
2þ to Mn
3þ driving a metal-insulator as well as a magnetic
transition. Hanif et al. have reported magnetic behavior in the case of Co-doped
CdSe nanocrystals [97], thus experimentally confirming the existence of magnetism in small sized nanocrystals.
0 10 20 30 40 50 60 70 80
0
1
2
0 10 20 30 40 50 60 70 80
0
1
2
3
4
0 10 20 30 40 50 60 70 80 90
0
1
2
3
0 10 20 30 40 50 60 70 80
0
1
2
0 10 20 30 40 50 60 70 80
0
1
2
3
4
0 10 20 30 40 50 60 70 80 90
0
1
2
3
Diameter (Å)
CdS
DE g
(eV)
CdSe
CdTe
ZnS
ZnSe
ZnTe
Fig. 11.11. The sp
3 d
5 TB model with the
cation–anion and anion–anion interactions
([75], solid line) compared with the sp
3 s* TB
nearest neighbor model ([76], dashed line), the
EMA model (dotted line) and the experimental
data points: CdS (a) [77], (s) [78], (S) [79],
(k) [99]; dSe (k) [80], (s) [81], (S) [82];
CdTe (k) [83], (s) [84], (S) [85]; ZnS (k)
[87], (s) [88], (y) [89], (a) [90], (S) [12]; ZnSe
(k) [91], (s) [16]; ZnTe (k) [92]. Adapted
from [75].
11.5 Electronic Structure Calculations 393