2. COMPUTATIONAL MODELS AND DETAILS
2.1.Computational models
BiOBr belongs to tetragonal crystal, and its space group is
P4/nmm
(NO.129)[19]. The atoms of primitive cell occupy
the following special positions: O in 2a (0, 0, 0),
Br in 2c with a fractional
parameter \(u_{\text{Br}}\)(0, 0.5, 0.653) and Bi also in 2c but with a
different parameter \(u_{\text{Bi}}\)(0, 0.5, 0.154). BiOBr crystal is
composed by alternative stacks of double Br slabs and
[Bi2O2]2+ slabs
along [001] direction into a tetragonal matlockite (PbFCl)
structure[20]. In order to study the influence of
electronic structure regulation visible-light response via 3d TMs doping
BiOBr, we adopted 3×2×2 supercell
with 72 atoms, because excessive metal doping may induce the appearance
of new recombination traps of photogeneratede −- h +pairs[18]. Here, 3d TMs-doped BiOBr systems are
built up through replacing one Bi atom located at the host of BiOBr
crystal lattice with 3d TM atom, corresponding to 4.167% atomic doping
content, as illustrated in Figure 1. The introduced TMs atoms are more
biased towards the O atom layer, which may be attributed to the
substitution of smaller radius for 3d TMs than Bi atom
rBi=1.17 Å[12].