Calculated  Other theory  Expt.  
HI  (a) 1.652, (b) 1.605  1.626  1.609 
I2  (a) 2.667, (b) 2.583  2.661  2.666 
HI (Expt.)  K. P. Huber and G. Herzberg, "Constants of Diatomic Molecules", Van Nostrand Reinhold, New York, 1979 
HI (Theory)  C. Hartwigsen, S. Goedecker, and J. Hutter, Phys. Rev. B 58, 3641 (1998) 
I2 (Expt.)  K. P. Huber and G. Herzberg, "Constants of Diatomic Molecules", Van Nostrand Reinhold, New York, 1979 
I2 (Theory)  C. Hartwigsen, S. Goedecker, and J. Hutter, Phys. Rev. B 58, 3641 (1998) 
Calculation conditions 

Version  OpenMX1.9 
Basis set  (a) I9.0s2p2d2, H5.0s2p1 
(b) I9.0s3p3d3, H5.0s3p2  
Pseudo potential  I_GGA.vps, H_GGA.vps as scalar relativistic VPS 
Functional  GGAPBE 
spinorbit coupling  None 
Spin noncollinearity  None 
Ecut  210 Ryd 