材料科学基础_02.ppt

材料科学基础Fundamental of Materials
Prof: Tian Min Bo
Tel: 62795426 ,62772851
E-mail: ******@.
Department of Material Science and Engineering
Tsinghua University. Beijing 100084
Lesson two
§ Atomic bonding
Ⅰ.Bonding forces and energies
FN : net force
FA : attractive force
FR : repulsive force
For atomic systems:
Bonding energies:
Ⅱ.Primary interatomic bonds
1. Ionic bonding
Ionic bonding is always found pounds that posed of both metallic and nonmetallic elements, elements that are situated at the horizontal extremities of the periodic table.
Interionic Forces
Z1, Z2=number of electrons removed or added from the atoms during the ion formation
e =electron charge
a =interionic separation distance
ε0=permittivity of free space=×10-12C2/(N·m2)
Interionic Energies
Attractive energy
Repulsive energy
Example problem  If the attractive force between a pair of Mg2+and S2- is ×10-8N and if the S2- ion has a radius of , calculate a value for the ionic radius of the Mg2+ ion in nanometers.
Solution