where R is the gas constant, N is the number of possible compositions. In conventional two-component alloys, the configuration entropy is R ln 2 ∼ 0.69R, but when the alloy becomes a five-component, the configuration entropy is ∼ 1.61R. The HEA material is defined by S > 1.5R, where a middle entropy alloy has 1.0R < S < 1.5R and a low entropy alloy S < 1.0R. In the case of normal two-component alloys, a phase separation usually occurs without enthalpically unfavorable alloying due to low configuration entropy. The phase formation is thermodynamically guided by the Gibs free energy of mixing ΔG = ΔH -T ΔS defined by the enthalpy ΔH and ΔS entropy parts at temperature T . In contrast, when the configuration entropy is increased, even under enthalpically unfavorable conditions, entropy acts as a driving force and a single-phase alloy forms (it is similar to the surfactant to oil/water emulsion formation). It has been reported that HEA conversion improves the mechanical strength of metals . Several reports on HEA using precious metals, including Kitagawa et al. and others , have reported that HEA has a greater catalytic effect than stand-alone palladium or platinum. However, up to now, HEA has not been adapted to optical devices based on optical/plasmonic properties.