Density function theory (DFT) method was developed and applied for fundamentally understanding the doping effect of various metals (Al, Ti and Cr) on vanadium dioxide (VO2). The substitution doping of Al, Ti and Cr in VO2 could lead to significant changes in electronic
structure, band gap and optical property. Different from physical experiments, the DFT method could be utilized for fundamental understandings at an atomic scale. It was found via DFT calculations that: (i) Al doping caused a slightly distorted octahedron in monoclinic VO2(M), and
narrowed the band gap of VO2(M) due to the upward shift of the valence band (VB), while Cr doping narrowed the band gap because of the downward shift of the conduction band (CB); (ii) Ti doping slightly widened the band gap of VO2(M); and (iii) the optical reflectivity
of VO2(M) decreased after substitution doping low-valent metals (e.g., Al). This study will be beneficial for designing and controlling elemental doping to obtain metal oxide nanocomposites with unique band gap and electronic structure for thermochromic energy saving applications.