Difference between revisions of "Intermolecular and interparticle forces"

From Soft-Matter
Jump to: navigation, search
(Interactions from molecular attraction)
Line 99: Line 99:
Israelachivili Fig.10.2
Israelachivili Fig.10.2
* (a) A moleucle near a flat surface.
* (a) A molecule near a flat surface.
* (b) A sphere near a flat surface.
* (b) A sphere near a flat surface.
* (c) Two flat surface.
* (c) Two flat surfaces.

Revision as of 16:55, 22 September 2008

Back to Topics.

Intermolecular energies

3D Pressure-volume isotherms 2D Spreading pressure-area isotherms
Hirschfelder Fig 4-1-1.gif Gaines Fig 4-7.gif
Hisrshfelder, Fig. 4.1.1 Gaines, Fig. 4.7

Flow properties from molecular energies

Vicosity at short times.png For short time scales and simple liquids.
Erying model of flow.png Erying model: When the strain is generated molecules are "trapped" and "jump" to a relaxed state. Relaxation time in Eyring model.png
Viscosity with Erying model.png ν is the characteristic frequency in the solid and ε is the heat of vaporization of the liquid.

Forces near surfaces

  • Bulk phases are characterized by density, free energy and entropy – not by forces.
  • Molecular forces average out.
  • Not so at surfaces.

Galileo Surface Forces.png Galileo reference.png

(Modern) forces near sufaces

  • (a) This potential is typical of vacuum interactions but is also common in liquids. Both molecules and particles attract each other.
  • (b) Molecules attract each other; particles effectively repel each other.
  • (c) Weak minimum. Molecules repel, particles attract.
  • (d) Molecules attract strongly, particles attract weakly.
  • (e) Molecules attract weakly, particles attract strongly.
  • (f) Molecules repel, particles repel.

Israelachvili Fig 10-1.gif
Israelachivili Fig.10.1

Interactions from molecular attraction

Eqn molecular attraction.png
Israelachvili Fig 10-2.gif
Israelachivili Fig.10.2

  • (a) A molecule near a flat surface.
  • (b) A sphere near a flat surface.
  • (c) Two flat surfaces.

Eqn Molecule surface attraction.png
Eqn Sphere Surface Attraction.png
Eqn Surface Surface Attraction.png

Derjaguin Force Approximation

Israelachvili Fig 10-3.gif
Israelachivili Fig.10.3
Eqn Derjaguin Force Equation.png
Eqn Derjaguin Force Equation-II.png

Where W(D)is the energy of interaction of two flat plates.

Back to Topics.