Exploring Hexagonal, Face-Centered & Body-Centered Packings

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Discussion Overview

The discussion focuses on the comparison of hexagonal closest packing (HCP), face-centered cubic packing (FCC), and body-centered cubic packing (BCC) in terms of their efficiency, volume, coordination number, packing, and density. Participants explore theoretical aspects and relationships between these packing structures.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant suggests that body-centered packing appears less efficient due to the arrangement of spheres, while hexagonal packing seems the most packed.
  • Another participant emphasizes the need to derive packing efficiency and notes that FCC and HCP are equally dense, although the math is not provided.
  • A participant expresses uncertainty about the relationship between coordination number, packing, and density, proposing that coordination number can be viewed as mass and packing as volume, leading to density as mass per volume.

Areas of Agreement / Disagreement

Participants express differing views on the efficiency of body-centered packing compared to hexagonal packing, and there is no consensus on the relationship between coordination number, packing, and density.

Contextual Notes

Participants have not resolved the mathematical relationships or provided explicit definitions for terms like packing efficiency and coordination number, which may limit the clarity of the discussion.

BH20
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Looking at hexagonal closest packing, face centred (or closest packing) and body-centered packing.

So I need to know abit about each.

I would think body-centered was the least efficient having looked at the arrangment. The main layer has to be centered a certain way to fit the rest..which means that he spheres are not close to each other but it looks more organized. Hexagonal looks the most packed to me.

I also need to know..in terms of volume how do thetwo more efficient ways of packing compare..and also what is the relationship between coordination number, packing and density (as mass/volume)?

Thanks
 
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anybody have any idea?
 
all of this should be explained explicitly in you text.
 
all of this should be explained explicitly in your text.

ignore the previous post, it seems that the deletion function is not working.
 
Last edited:
Your text must also teach you how to derive the packing efficency/fraction. Once, you learn how this works, it's fairly simple to show that the FCC and HCP are both equally dense. Without actually doing the math, it's hard to compare pqacking efficiency.
 
Ok, I figured that part out.

I still don't see the relationship between coordination number, packing and density. (as mass/volume)

This is what I wrote: (makes sense to me, but I could be way off)


We can look at coordination number as mass, because it is the number of atoms
that are packed around the space lattices. While the packing refers to the volume since the type of packing is the way the spheres are structured. If they are placed a certain way they will occupy a bigger or lower volume. The density
is the relationship between those two (the mass per volume).
 

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