The influence of La substitution can then be further investigated from the calculated atomic effective charge and bond length of BixLa1−xFeO3 solid solution. Notably, as obtained from Mulliken population analysis, the calculated effective charge of Bi and La atoms increased when La concentration increased, whereas the calculated effective charge of Fe BAM 22P decreased when La concentration increased. Larger effective charge represents the less covalent bonding. The substitution of La atom at the Bi side reduced the influence of stereo-chemically active lone pair of Bi 6s electrons which vanished at high level of La concentration ratio of 0.75 and 1.00. Then, less covalent Bi–O and La–O bonding and more covalent Fe–O bonding can be confirmed by the labia majora calculated bond length. Notably, the calculated bond length of Bi–O and La–O bonding increased when La concentration increased. The calculated bond length for Fe–O decreased when La concentration increased. Decrease in the covalency degree of Bi–O and La–O bonding with increased La concentration may be associated to the smaller electronegativity value of La (1.10) than Bi (2.02) atoms.