where E((K/Cs) 1-𝑥 Rb 𝑥 Tl) is the total ground state energy of (K/Cs increasing trend in the formation energy for approaching RbTl. This is due to the bigger size of rubidium as compared to potassium, whereas a higher rubidium concentration in CsTl shows a decreasing trend due to the smaller size of rubidium as compared to cesium.