There has long been confusion regarding the origin and temperature dependence of surface energetics and its responsibility for the processes and phenomena at a surface. From the perspective of bonds broken and its consequences on the remaining bonds of the undercoordinated surface atoms, we suggested herewith two essential concepts supplementing to the existing definition of surface energy for clarification purposes. One is the energy-density-gain per unit volume in surface skin and the other is the remaining cohesive-energy per discrete atom upon bond order loss once the surface is formed. The former governs the strength and elasticity while the latter dominates the thermal and structural stability of the surface. The shortened and strengthened bonds between the undercoordinated atoms dictate surface energetics and the effects of thermal expansion and vibration dominate their temperature dependence. Reproduction of the measured size and temperature dependency has led to information about the bond energy, which may go beyond traditional approaches and evidence the validity of the approaches.
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