Solids--arrangement of atoms in lattice

[ravi_i2h]

Which unit cell do we obtain if spheres are arranged in ABAB type in 2D but AAAA type in 3D?

Arranging spheres ABAB type in 2D gives us close packing.
Now, this layer if arranged in ABAB (in 3D) gives us HCP and if arranged in ABC (in 3D) gives us FCC. What do we get if we arrange it in AAA type (in 3D) ?
Please help. I have been struggling with this question for a long time.

[deleted-2131]

Hi ravi_i2h,

I'm a bit unclear about what, exactly, your question is, but I will answer the question I think you are asking. Assuming only one type of sphere, AAA stacking of hexagonal closest packed layers (i.e., stacking identical layers on top of one another so that the center of each sphere lies directly over the center of the spheres on every one of the lower layers) would give you a simple cubic (sometimes called primitive cubic) unit cell.

Since these forums are designated for students, parents, and teachers working on science fair projects, what is the hypothesis you will test?

[ravi_i2h]

Hi ravi_i2h,

I'm a bit unclear about what, exactly, your question is, but I will answer the question I think you are asking. Assuming only one type of sphere, AAA stacking of hexagonal closest packed layers (i.e., stacking identical layers on top of one another so that the center of each sphere lies directly over the center of the spheres on every one of the lower layers) would give you a simple cubic (sometimes called primitive cubic) unit cell.

Since these forums are designated for students, parents, and teachers working on science fair projects, what is the hypothesis you will test?

Hi Terik,
We are talking about one type of spheres only.

ABABAB in 2D refers to the relative arrangement of lines of atoms in two dimension.

AAAAAA in 3D means the relative arrangement of those layers in three dimension (i.e. stacking layers on top of another so that the center of each sphere lies directly over the center of the spheres on every one of the lower layers).


AAAAAA in 2D and AAAAAA in 3D gives us simple cubic (sometimes called primitive cubic) unit cell. (no doubt about that)
What does ABABAB in 2D and AAAAA in 3D give?

While studying solids, i was trying to derive relationship between the unit cells we are studying and the relative arrangement of spheres (atoms) that would give us those unit cells. This question is not related to any experimental fair project. Maybe,i should not have had asked it here. sorry for bothering.