Lanthanum phosphide is an example of a strongly correlated material,[3] complicating theoretical prediction of its properties.

According to HSE06 calculations, lanthanum phosphide has been theoretically predicted to have an indirect band gap of 0.25 eV along the Γ-X direction.

[5] Using EVGGA, the compound is predicted to have a band gap of 0.56 eV along the Γ-X direction.

[6] FP-LAPW has predicted an indirect gap of 0.33 eV along the Γ-X direction.

[7][8] In addition to the simple phosphide, LaP, lanthanum and phosphorus can also form phosphorus-rich compounds such as LaP2[9] LaP5[10] and LaP7.