A error

[mldavidhuang]

I was using ATK to calculate a system consisting of two layers of graphene nanoribbon with the interlayer distance is 8 Angstrom(the script of my model is attached) ,but as the calculation began there is error as follows, could anyone explain to me what is the problam?

                           |--------------------------------------------------|
Calculating Eigenvalues    :

** Back Engine Exception 541 : Diagonalization error, overlap matrix not positive definite, try to increase interaction_max_range
** Location : mathutils.cpp:1123


This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
NanoLanguageScript execution failure

[zh]

A similar problem has been discussed here:
http://quantumwise.com/forum/index.php?topic=853.0

I tested the configuration in your script file using the SZP basis set. It works well.

[mldavidhuang]

But could you tell me how to increase the interaction_max_range ?  I find no such parameter in the calculator settings

[Anders Blom]

It's under "Numerical Accuracy Parameters" for Huckel, but not relevant for DFT.

8 Å seems rather extreme, it means the two layers are not interacting, so you might as well just have one...

[mldavidhuang]

But I want to compare the properties of bilayer GNR 's dependence for interlayer distance. you mean such interlayer distance is not reasonable for a two layer system? So it is meaningless, right?

[Anders Blom]

This distance is so large that you essentially have decoupled sheets. That's not meaningless, but don't go larger, just smaller. Reasonable interlayer distances lie in the range up to 5 Å, at you can easily find in the literature, e.g. APL 92, 223106 (2008)

[mldavidhuang]

Thanks for your answer and  reference!