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General Questions and Answers / Grain Boundaries
« on: July 30, 2017, 02:44 »
Hi all,
I am trying to model some tilt grain boundaries. Two questions.
First:
I have seen the transport tutorial for creating a GB and that I managed fine, since it is just slicing two different planes. I am having issues with creating symmetric tilt boundaries. For instance the special case of a Σ3, where the grains are both in a (110) orientation with (-1 1 1)//(-1 1 -1). If I use the cleave tool for the two different {111} planes, then it returns two crystals of the same orientation. So, when I build the "interface" using the interface tool, their is no miss-orientation (ie I am joining two identical cells). I have also though about taking the initial FCC crystal and rotating, but it only has one atom in the basis, so the function changes nothing (rotate operates on the basis vectors not lattice). Using repeat then rotating gives the correct orientation, but then wrapping or using the interface tool causes some odd overlap within the rotated cell (since the rotated basis is not contained within the un-rotated lattice). Does anyone have any ideas, or has anyone here modeled grain boundaries before?
I saw this thread with a the paper by Feldman https://quantumwise.com/forum/index.php?topic=1541.msg7699#msg7699. The two twin grain boundaries he molded would be a great start for me. I see that I can use the CSL model while constructing the interface. If I want say Σ3, should I cleave (-1 1 1)&(-1 1 -1) then scan a rotation of 69 degree to 72 degree?
Second question:
After creating and relaxing a GB I would like to define a portion of the GB as a cell, then run some phonon calculations. How do I define the cell?
Thank you
Eric Hoglund
University of Virginia
I am trying to model some tilt grain boundaries. Two questions.
First:
I have seen the transport tutorial for creating a GB and that I managed fine, since it is just slicing two different planes. I am having issues with creating symmetric tilt boundaries. For instance the special case of a Σ3, where the grains are both in a (110) orientation with (-1 1 1)//(-1 1 -1). If I use the cleave tool for the two different {111} planes, then it returns two crystals of the same orientation. So, when I build the "interface" using the interface tool, their is no miss-orientation (ie I am joining two identical cells). I have also though about taking the initial FCC crystal and rotating, but it only has one atom in the basis, so the function changes nothing (rotate operates on the basis vectors not lattice). Using repeat then rotating gives the correct orientation, but then wrapping or using the interface tool causes some odd overlap within the rotated cell (since the rotated basis is not contained within the un-rotated lattice). Does anyone have any ideas, or has anyone here modeled grain boundaries before?
I saw this thread with a the paper by Feldman https://quantumwise.com/forum/index.php?topic=1541.msg7699#msg7699. The two twin grain boundaries he molded would be a great start for me. I see that I can use the CSL model while constructing the interface. If I want say Σ3, should I cleave (-1 1 1)&(-1 1 -1) then scan a rotation of 69 degree to 72 degree?
Second question:
After creating and relaxing a GB I would like to define a portion of the GB as a cell, then run some phonon calculations. How do I define the cell?
Thank you
Eric Hoglund
University of Virginia