Opti and thermal conductivity for SLG(single layer graphite)

Hi ,everyone
I’m new to gulp,i’m learning example1 &example67 for SLG(Single Layer Graphene),however there are two WARNING from the output of the first .gin file
“WARNING : ill conditioned Hessian - using diagonal elements only”
“WARNING : Properties cannot be calculated - matrix is singular”
and the result of the thermal conductivity is 121 W/mK ,which should be 2000 W/mK from the literature.
i have been working for two months without anything useful ,does anyone have any idea?

here are my input files

graphite.gin (263 Bytes)
c_singlelayer.gin (441 Bytes)
runalamode (4.2 KB)
NB:

  1. runalamode is a script for running gulp with alamode (from the internet),i donot know how to run alamode without the script.
    2.Forgive me for my poor English, sry.

The ill-conditioned Hessian and singular matrix for properties tells you that you have a model where there are two or more fragments that have no interaction with each other & so it makes no sense to treat the system as being a 3-D solid. This is a classic mistake for graphite and means you are using a model where there are no interactions between the layers (in your case Tersoff). You should run the system as a 2-D model to avoid this.
As for computing thermal conductivity, this is one of the most complex properties to work on & so I’d suggest you become more familiar with simulation methods first before trying the most difficult thing. Your supervisor should be able to explain the different approaches to thermal conductivity and why models might not always agree with experiment.

Hi,julian
Thanks for your advice, thank you so much,but how can i run the system as a 2-D model(SLG) ,in my case i thought i was dealing a system of SLG ,maybe there is some keyword or option ,or maybe i didn’t use a proper structure for SLG?
By the way, I just found that the script is from Julian Gale( :smiley:),i was wondering if there is any tutor for the script or a new edition
thank you again!
sincerely,

Blockquote

Isn’t a “single layer graphite” just graphene? If so, this is fundamentally 2D from the start. How to run 0, 1, 2 and 3-D systems is covered in the GULP manual and help.txt/help.html files - it’s just a matter of inputing using a 2-D (surface) cell.
There isn’t a new version of the script and in principle you don’t need it, as GULP can call Alamode directly (see example files). Of course this relies on you having install Alamode on your system (use the versions as noted in the README if you want to guarantee compatability) and having set the environment variable to point to where it is (again, as per the README file).