Explaining Intermolecular Forces at the Quantum Level

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SUMMARY

This discussion centers on the quantum-level explanations of intermolecular forces, specifically addressing adhesion, cohesion, tensile strength, stiffness, strain energy, vibration, and the effects of temperature and pressure on these forces. The term "van der Waals" forces is highlighted as encompassing all intermolecular forces, excluding hydrogen bonding. The complexity of the topic is acknowledged, with a recommendation for further reading in quantum chemistry and solid-state physics to gain a comprehensive understanding of these mechanical properties.

PREREQUISITES
  • Quantum chemistry fundamentals
  • Solid-state physics principles
  • Mechanical properties of materials
  • Understanding of intermolecular forces
NEXT STEPS
  • Study "Quantum Chemistry" textbooks for detailed explanations of intermolecular forces
  • Research "Solid-State Physics" to understand material properties at the quantum level
  • Explore "Young's Modulus" and its applications in structural engineering
  • Investigate the effects of temperature on "van der Waals" forces in materials
USEFUL FOR

Structural engineers, materials scientists, and anyone interested in the mechanical properties of materials at the quantum level will benefit from this discussion.

mdshameer
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Can someone enlighten me about the quantum level explanations for the following:
1. Adhesion between two substances
2. Cohesion within a substance
3. Strength of a substance (as in tensile strength, compressive strength and shear strength)
4. Stiffness of a substance (as in Youngs modulus, Poissons ratio and shear modulus)
5. Strain energy of materials
6. Vibration and damping of strain energy systems
7. Variation of inter molecular forces with tempearture (as in melting and boiling)
8. Variation of intermolecular forces with external pressure
9. Absence of intermolecular forces between two soilds however closely they are spaced
Hope that I have expressed my queries clearly.
Regards
 
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"van der Waals" forces, in its original and most general form, refers to essentially all intermolecular forces (except possibly hydrogen-bonding, which at least in practice is excluded even from the most general usages these days). You might want to start http://en.wikipedia.org/wiki/Intermolecular_force" .

There certainly exists quantum-level explanations for all that, but there's no way it could be summarized in a single message-board post. You're basically asking for a complete quantum description of most chemical and material properties, which is something that encompasses several whole fields (quantum chemistry, solid-state physics). So you'd really need several whole textbooks to get the details.

I'm not sure what you mean by (9) though. There are always intermolecular forces, even at a large distance (at the very least there are always London forces).
 
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Dear Alxm, thanks for the reply.
I am however, not asking for a complete description of most chemical and material properties. I am a structural engineer by profession and am interested only in the mechanical properties of a continuum. Besides, I am not also looking for a detailed description - sources are more than sufficient. Unfortunately, I could not dig out muc from the net, myself.
The 9 th point is the particular position that puzzles. Please forgive me if I am wrong. Suppose, I take two bars of steel and place them extremely close side-by-side. Intutively I feel that the forces between molecules within one bar and the forces between close molecules from bar-to-bar are different. If so, what is the origin of such difference?
I hope I have made the query clear
Regards
 

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