Magnetic, Electronic, and Optical Studies of Gd-Doped WO 3 : A First Principle Study.

Tungsten trioxide (WO 3 ) is mainly studied as an electrochromic material and received attention due to N-type oxide-based semiconductors. The magnetic, structural, and optical behavior of pristine WO 3 and gadolinium (Gd)-doped WO 3 are being investigated using density functional theory. For exchange-correlation potential energy, generalized gradient approximation (GGA+U) is used in our calculations, where U is the Hubbard potential. The estimated bandgap of pure WO 3 is 2.5 eV. After the doping of Gd, some states cross the Fermi level, and WO 3 acts as a degenerate semiconductor with a 2 eV bandgap. Spin-polarized calculations show that the system is antiferromagnetic in its ground state. The WO 3 material is a semiconductor, as there is a bandgap of 2.5 eV between the valence and conduction bands. The Gd-doped WO 3 's band structure shows few states across the Fermi level, which means that the material is metal or semimetal. After the doping of Gd, WO 3 becomes the degenerate semiconductor with a bandgap of 2 eV. The energy difference between ferromagnetic (FM) and antiferromagnetic (AFM) configurations is negative, so the Gd-doped WO 3 system is AFM. The pure WO 3 is nonmagnetic, where the magnetic moment in the system after doping Gd is 9.5599575 μB.