Table 1 Lattice parameters, energy gaps, our calculated ${\epsilon }_1^{\perp }\left(0\right)$ and ${\epsilon }_2^{II}\left(0\right)$ and Δn(0).

A (Å)

5.52^a

5.78^a

6.179^a

C (Å)

11.08^a

11.57^a

12.36^a

$E_g^{\exp .}$ (eV)

1.53^{b, r}, 1.55^e, 1.48ⁱ, 1.54^d

1.04^b, 0.96^g, 1.01^h, 0.98^{i, r}, 0.88^d

1.06^{b, j}, 0.96^f

$E_g^{Theory}$ (eV)

0.01^c, -0.14^r, 0.812*

0.01^c, -0.2^r, 0.416*

0.18^c, 0.424*

${\epsilon }_1^{\perp }\left(0\right)$

11.3*, 9.71^p, 8.6^q

14.8*

13.5*

${\epsilon }_1^{II}\left(0\right)$

11*, 9.68^p, 8.4^q

14.6*

13.8*

Δn(0)

-0.018^k, -0.019*

-0.012^m, -0.013*

0.002*

N ₀

2.532^{n, o}, 2.71*

2.606ⁿ, 2.83*

2.720ⁿ, 2.91*