Atom Energy in Crystals: Gibbs Free Energy

In summary, the energy per atom in a solid can be ambiguous, with surface atoms typically having a higher potential energy due to being under-coordinated. There is no general conclusion about the vibrational free energy or stress-volume energy of the surface. Additionally, the electric potential energy of surface atoms is higher than those in the bulk due to inward electric force. The excess energy of surface atoms is known as the "unrelaxed" surface energy.
  • #1
aaaa202
1,169
2
Does atom at the surface of a crystal have more or less energy than those in the bulk? And how does this relate to their Gibbs free energy?
 
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  • #2
The notion of energy per atom in a solid is a bit ambiguous.
The surface atoms are under-coordinated (less number of bonds), thus it is expected that the average potential energy on the surface should be higher compared to the bulk.
I do not recall any general conclusion about the vibrational free energy of the surface or its stress-volume energy.
 
  • #3
At atom at the surface has a higher electrical PE than an atom in the bulk. This is because the electric force on the atom is inward.
 
  • #4
So is the surface energy simple the excess energy that the surface atoms have due to unsaturated Bonds?
 
  • #5
aaaa202 said:
So is the surface energy simple the excess energy that the surface atoms have due to unsaturated Bonds?

This is the "unrelaxed" surface energy.
 

1. What is Gibbs Free Energy?

Gibbs Free Energy is a thermodynamic quantity that measures the amount of energy available to do work in a system at constant temperature and pressure. It takes into account both the enthalpy (heat energy) and entropy (disorder or randomness) of a system.

2. How does Gibbs Free Energy relate to atom energy in crystals?

Gibbs Free Energy is a crucial factor in determining the stability and formation of crystals. In a crystal, atoms are arranged in a highly ordered and stable lattice structure. The Gibbs Free Energy of a crystal is the energy required to break apart the crystal and disperse its atoms, which is known as the lattice energy. This energy must be overcome in order to form a crystal, and the lower the Gibbs Free Energy, the more stable the crystal.

3. What is the significance of atom energy in crystals?

Atom energy in crystals is significant because it plays a role in various physical and chemical properties of crystals, such as their melting point, hardness, and electrical conductivity. It also determines the stability and formation of crystals, which is important in fields such as material science and solid state chemistry.

4. How is Gibbs Free Energy calculated for atom energy in crystals?

The Gibbs Free Energy of a crystal can be calculated using the Gibbs-Helmholtz equation, which is ΔG = ΔH - TΔS. ΔH is the change in enthalpy, or heat energy, of the crystal, and ΔS is the change in entropy, or disorder, of the crystal. T is the temperature in Kelvin. This equation takes into account the energy changes that occur during the formation or dissolution of a crystal.

5. What factors can affect the Gibbs Free Energy of a crystal?

The Gibbs Free Energy of a crystal can be affected by changes in temperature, pressure, and the chemical composition of the crystal. Temperature and pressure can alter the enthalpy and entropy of the crystal, while changes in the composition of the crystal can affect its lattice energy. Additionally, the presence of impurities or defects in the crystal can also influence its Gibbs Free Energy.

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