QuantumATK Forum
QuantumATK => General Questions and Answers => Topic started by: huangshenjie on January 11, 2013, 03:55
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Dear all, I want to learn something about the converge and I have seen a lot of posts about converge problem which mention a tutorial named Convergence Tricks. But I cannot find it.
Thank you in advance!
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The tutorial is still available physically (here (http://quantumwise.com/documents/tutorials/2008.10/FeMgO Convergence Tricks.pdf)) but as the title etc indicates, it applies mostly to the older versions of the software, and to some extent to the specific FeMgO system which was hard to converge before we introduced the double contour integration and a more correct treatment of the spill-in terms.
In ATK 12.2 and later, convergence problems are almost invariably related to either too few k-points or a too short electrode (or, perhaps, too short screening region), unless of course the geometry is unusual and complicated.
At high bias you need a longer screening region. A rather special trick which can also help at high bias is to use a smaller value for the "real_axis_point_density".
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The tutorial is still available physically (http://quantumwise.com/documents/tutorials/2008.10/FeMgO Convergence Tricks.pdf) but as the title etc indicates, it applies mostly to the older versions of the software, and to some extent to the specific FeMgO system which was hard to converge before we introduced the double contour integration and a more correct treatment of the spill-in terms.
In ATK 12.2 and later, convergence problems are almost invariably related to either too few k-points or a too short electrode (or, perhaps, too short screening region), unless of course the geometry is unusual and complicated.
At high bias you need a longer screening region. A rather special trick which can also help at high bias is to use a smaller value for the "real_axis_point_density".
Thanks a lot. However, I tried to open the link you provided, it shows error 404 Notfoundium……
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Link fixed (contained spaces)