A halide scintillator material is disclosed. The material is single-crystalline and has a composition of the formula A3MBr6(1-x)Cl6x (such as Cs3CeBr6(1-x)Cl6x) or AM2Br7(1-x)Cl7x (such as CsCe2Br7(1-x)Cl7x), 0≦x≦1, wherein A consists essentially of Li, Na K, Rb, Cs or any combination thereof, and M consists essentially of Ce, Sc, Y, La, Lu, Gd, Pr, Tb, Yb, Nd or any combination thereof. Furthermore, a method of making halide scintillator materials of the above-mentioned compositions is disclosed. In one example, high-purity starting halides (such as CsBr, CeBr3, CsCl and CeCl3) are mixed and melted to synthesize a compound of the desired composition of the scintillator material. A single crystal of the scintillator material is then grown from the synthesized compound by the Bridgman method. The disclosed scintillator materials are suitable for making scintillation detectors used in applications such as medical imaging and homeland security.