FCC Crystal Problem: Nearest Neighbors, Bond Angles & Packing Fraction

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Homework Help Overview

The discussion revolves around a problem related to face-centered cubic (FCC) crystal structures, specifically focusing on the number of nearest neighbors, bond angles, and packing fraction. Participants express confusion regarding the concepts and calculations involved.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to understand the packing fraction and seeks clarification on terminology, indicating uncertainty about where to begin. Other participants provide brief responses, with one suggesting the term "atomic packing factor" as an alternative. Another participant shares a calculation for the packing fraction but seeks validation for their answer.

Discussion Status

The discussion is ongoing, with participants exploring different aspects of the problem. Some guidance has been offered regarding terminology, and a calculation has been presented, though it has prompted a request for validation rather than reaching a consensus.

Contextual Notes

The original poster mentions difficulty finding information in their textbook, suggesting potential gaps in resources or terminology that may affect their understanding of the topic.

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Homework Statement



Write down the number of nearest neighbours in a FCC structure, calculate the angle between the bonds and the packing fraction.

Homework Equations



Literally don't know where to start!

The Attempt at a Solution



Very confused at the moment. Tried to look up packing fraction in my Solid State texbook - but it isn't there?! Is there another name for it? Can someone point me in the right direction please? :)
 
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ok - could someone validate my answer please?

i got 4 atoms in one crystal,

the volume of one atom: ( pi * (2^(3/2)) * (a^3) ) / 48

the volume of the crystal is a^3

giving a packing fraction of 0.236?
 
Check your math.
 

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