1. What happens when the angles between the three sides of a trigonal reach 120degrees?(adsbygoogle = window.adsbygoogle || []).push({});

I know that at 90degrees, it becomes a simple cubic. At 109degrees, it becomes a body centered cubic. At 60 degrees, it becomes a face centered cubic.

What about 120degrees? I think that perhaps it should form a structure like a football?

2. Can pentagons form a lattice? I know that regular pentagons don’t satisfy translational symmetry. But can any pentagon with different side lengths form a lattice?

I tried making one, but no pentagon satisfies the translation symmetry.

Many thanks.

- Farrukh

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# Homework Help: Trigonal lattice with each angle equal to 120degree

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