Band gap of rutile TiO2 (Expt.)  J. Pascual et al., PRL 39, 1490 (1977). 
Band gap of rutile of TiO2 (Theory)  K. M. Glassford and J. R. Chelikowsky, PRB 45, 3874 (1992). 
Calculation conditions 

Version  OpenMX3.0 
Basis set  Ti6.0Rs2p2d1, O5.0s2p2d1 
Pseudo potential  Ti_LDA.vps, Ti_GGA, and O_LDA.vps as scalar relativistic VPS 
Functional  LDA and GGAPBE 
spinorbit coupling  None 
Spin noncollinearity  None 
Ecut for hcp Ti  32 x 32 x 32 (about 450 Ryd, the fixed scheme is used) 
Ecut for rutile TiO2  180 Ryd 
kpoint  7 x 7 x 7 