### Author Topic: The construction of a two-dimensional material  (Read 180 times)

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#### Bertha_He

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##### The construction of a two-dimensional material
« on: August 9, 2019, 05:56 »
Dear experts,
I am using the 2016.04 version of ATK to build a two-dimensional material that is not in the material library.
Now I have some problems and need your help.
I consulted the literature and constructed this two-dimensional material according to the method in the case guide
(https://docs.quantumwise.com/tutorials/opening_a_band_gap/opening_a_band_gap.html).
After the structure optimization, I get lattice constants similar to those in the references, but there is no bond between atoms.
After trying, I found that when I changed Graphics-property-Fuzz factor in the Builder, keys would appear between the atoms
when the default parameter 1.10 in the Fuzz factor was changed to 1.15.
There's another case, when I change the value of KA in the K sample in New Calculator, when the value of KA is fixed to a value, the atoms will bond;
When you change KA to something else, there are no bonds between the atoms and the lattice constant changes；
The lattice constant will be fixed to other values, but this value will be quite different from the value in the literature.
I wonder why? How do I deal with this situation?
Is it reliable to change the keys of Fuzz factor?Can I use this model for that?

Thanks

#### Jess Wellendorff

• QuantumWise Staff
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##### Re: The construction of a two-dimensional material
« Reply #1 on: August 12, 2019, 15:23 »
Dear Bertha,
the fuzz factor simply determines how close two atoms must be in order for the GUI to draw a bond between them, so it is safe to tune it a bit according to chemical intuition. As for the k-point sampling along direction A, the equilibrium lattice constant should converge to a constant value as k_A increases, so you should probably check that.