Stable Compositions, Structures and Electronic Properties in K–Ga Systems Under Pressure

New stable stoichiometries in K–Ga systems are firstly investigated up to 100 GPa by the unbiased structure searching techniques. Six novel compositions as K_4Ga, K_3Ga, K_2Ga, KGa, KGa_2 and KGa_4 are found to be thermodynamically stable under pressure. Most of the predicted stable phases exhibit metallic character, while the Fd\bar3m KGa phase behaves as a semiconductor with a bandgap \sim 1.62 eV. Notably, the gallium atoms exhibit different interesting morphologies; e.g., Ga_2 units, zigzag chains, six rings and cage. We further investigate the bonding nature of K–Ga systems with help of electron localization function and Bader charge analyses. Strong covalent bonding characteristics are found between the Ga and Ga atoms, and ionic bonding patterns are observed between the K and Ga atoms. Meanwhile, we notice charge transferring from the K atom to the Ga atom in the K–Ga systems. The present results can be helpful for understanding the diverse structures and properties of K–Ga binary compounds at high pressures.