5. Dispersion Interactions- Macroscopic Bodies

Question 1

What is the Hamaker constant?

Answer 1

A geometry-independent constant that is used to quantify the strength of an interaction between two materials

Question 2

Give the equation for the Hamaker constant

Answer 2

A = Hamaker constant
n = density of atoms
C = constant

Question 3

Give the equation for the dispersion interaction energy between a flat slab and a semi-infinite solid

Answer 3

U(D) = dispersion interaction energy
A = Hamaker constant
S = slab area
D = separation distance

Question 4

Give the equation for the dispersion interaction energy between a sphere and a semi-infinite solid

Answer 4

U(D) = dispersion interaction energy
A = Hamaker constant
R = radius
D = separation distance

Question 5

Give the equation for the dispersion interaction force between a flat slab and a semi-infinite solid

Answer 5

F(D) = dispersion force
U = dispersion interaction energy
A = Hamaker constant
S = slab area
D = separation distance

Question 6

Give the equation for the dispersion interaction force between a sphere and a semi-infinite solid

Answer 6

F(D) = dispersion force
U = dispersion interaction energy
A = Hamaker constant
R = Radius
D = separation distance

Question 7

For a given geometry, the strength of the dispersion interaction (A₁₂) can be determined by ________ ______.

Answer 7

Measuring forces

Question 8

What is the typical range of the Hamaker constant?

Answer 8

Question 9

Why are approximations of the forces between two surfaces often inaccurate?

Answer 9

Surfaces are modelled as being perfectly flat when in reality they are really rough on the nanoscale. This means that the area of contact between two surfaces is actually very small.