α

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Exp.

a (Å)

3.865

3.861

3.856

3.854

3.851

3.842

3.841

3.830

3.904 [15]

c (Å)

4.034

4.053

4.070

4.084

4.107

4.157

4.170

4.233

4.158

c/a

1.044

1.050

1.055

1.060

1.067

1.082

1.086

1.105

1.065

E_gap (eV)

1.47

1.73

1.97

2.21

2.46

2.76

3.03

3.35

3.4 [16]