Lecture 1 Flashcards
What is the first term for the atomic interaction/potential energy?
Attraction (negative energy)
What is the second term for the atomic interaction/potential energy?
Repulsion (positive energy)
What happens when dU/dr = 0?
at r0 (equilibrium bond length), potential energy is minimized meaning attractive and repulsive forces balance
How does force behave at different separations r?
If r = r0 then net force is 0 (equilibrium)
If r < r0 then repulsive force dominates
if r > r0 then attractive force dominates
What are the 4 types of atomic bonding?
- Metallic
- Ionic
- Covalent
- Van der Waals
What are metallic bonds?
A metallic bond occurs when valence electrons delocalize and move freely among metal atoms, forming an “electron sea” that holds the metal atoms together
What are the key properties of metallic bonds?
-High electrical conductivity
-High thermal conductivity
-Good ductility
What are Ionic bonds?
Valence electrons transfer from a metal atom (which becomes a cation +) to a non metal atom (which becomes an anion - ). Electrons are not mobile.
What are the key properties of ionic bonds?
- Strong bonds due to their high melting points
- Low electrical conductivity
- Low thermal conductivity
What is a covalent bond?
Valance electrons are shared between neighboring atoms so each atoms can have a stable electronic configuration
What types of materials have covalent bonds?
- ceramics
- semiconductors
- insulators
What are the key properties of covalent bonds?
- strong bonds due to high melting point
- low electrical conductivity
- high thermal conductivity
What are Van der Waals bonds?
Adjacent atoms or groups of atoms that act as electric dipoles
What are key properties of VDWs?
- very weak due to its low melting point
-low electrical and thermal conductivities
As bond strength/energy increases what happens to the melting point?
It increases
How many crystal systems are there?
7
What is the notation for a specific plane?
(110)
What is the notation for a family of equivalent planes?
{110}
What is the notation for a specific direction?
[110]
What is the notation for a family of equivalent directions?
<110>
What does anisotropic mean?
Material properties can depend on crystal direction
With miller indices, what does a bar sign mean?
A negative value for either direction or plane
