August 05, 2024, 08:35:19 AM
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### Topic: Crystalline Solids  (Read 2570 times)

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#### Luna101

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##### Crystalline Solids
« on: February 16, 2021, 07:06:08 PM »
Hi please help me sketch the unit cell, determine the lattice shape and the number of “atoms” in the unit cell in the picture. Thanks in advance!

#### Babcock_Hall

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##### Re: Crystalline Solids
« Reply #1 on: February 16, 2021, 08:25:24 PM »
Would you show us your attempts?  A good place to start is by defining what a unit cell is.

#### Luna101

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##### Re: Crystalline Solids
« Reply #2 on: February 16, 2021, 08:35:32 PM »
I did the regular shapes like cube, Triangles and rectangle but the patterns I don't know where to start

#### Babcock_Hall

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##### Re: Crystalline Solids
« Reply #3 on: February 17, 2021, 10:09:23 AM »
Start with the definition of a unit cell, and apply it to each example.  In problems such as these there is typically more than one right answer.

#### Luna101

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##### Re: Crystalline Solids
« Reply #4 on: February 17, 2021, 10:13:12 AM »
Ok can you please show me at least an example from the patterns??

#### AWK

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##### Re: Crystalline Solids
« Reply #5 on: February 17, 2021, 10:42:48 AM »
You have to find unit cells of two-dimensional space groups (or the bases of parallelepipeds of three-dimensional groups)
The base of a unit cell can be as small as possible a square, rectangle, rhombus, or parallelogram. It is often possible to select another cell with the same area (two-dimensional).
Search your crystallography textbook for plane symmetry group (s) or Wikipedia for Wallpaper group (very complex explanation).
AWK

#### Luna101

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##### Re: Crystalline Solids
« Reply #6 on: February 17, 2021, 12:47:47 PM »
Please please just do one example from the picture so I can refer to it when I do the other problems please

#### AWK

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##### Re: Crystalline Solids
« Reply #7 on: February 17, 2021, 02:15:53 PM »
Look at the layer of the NaCl structure closest to you. Does that remind you of anything?
AWK

#### Luna101

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##### Re: Crystalline Solids
« Reply #8 on: February 17, 2021, 02:23:17 PM »
Is is supposed to represent pattern #2 or #4?

#### AWK

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##### Re: Crystalline Solids
« Reply #9 on: February 17, 2021, 02:46:50 PM »
Patern 2 has identical elements!
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#### Luna101

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##### Re: Crystalline Solids
« Reply #10 on: February 17, 2021, 02:48:17 PM »
Oh ok thanks. I figure out pattern 3 and 4 but I’m not sure about pattern 1,5,6

#### Luna101

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##### Re: Crystalline Solids
« Reply #11 on: February 17, 2021, 08:48:25 PM »
Never mind I figured it out