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Re^5: How to setup calculations for a twisted nanoribbon or bilayer graphene?

Siddheshwar Chopra
sidhusai@gmail.com


Dear Alex,
Thank you for the information that there is negligible difference in CPU times for DFT and TDDFT. Sir please have a look at the attached output file. I am unable to run this bilayer graphene file due to the error:

ERROR: BAD DELOCALIZED COORDINATES GENERATED!!!
       588 PRIMITIVE INTERNAL COORDINATES ARE BEING USED.
       252 LINEARLY INDEPENDENT COMBINATIONS OF THESE ARE FOUND.
       258 COORDINATES ARE NEEDED TO HAVE A TOTAL OF 3N-6 OR 5.

IF THE NUMBER OF LINEARLY INDEPENDENT COOORDS IS TOO SMALL,
ADD SOME COORDINATES BY -NONVDW- TO CONNECT MONOMER PIECES
(ESPECIALLY IF YOU ARE SHORT BY A MULTIPLE OF 6), OR ELSE
USE -IXZMAT- TO ADD EXTRA PRIMITIVE COORDINATES.

IF THE NUMBER OF LINEARLY INDEPENDENT COOORDS IS TOO BIG,
TRY USING -IRZMAT- TO REMOVE SOME PRIMITIVE COORDINATES.

I also rea the manual, but failed to understand how to use "NONVDW". Please help me in running this input file. Where am I doing wrong?
Also I wish to know that DO we run the optimization with DIFFERENT distances between layers and then find the lowest energy one OR the optimization started with ANY distance between the layers will automatically get it to the lowest energy configuration? I strongly feel the latter one is correct.

Kind Regards,


On Tue Oct 14 '14 9:20pm, Alex Granovsky wrote
----------------------------------------------
>Dear Siddheshwar,

>I'd suggest you to create a realistic model of bilayer graphene,
>then to optimize it using DFT with a dispersion correction.
>Use of DFTD is documented in the manual. The difference in CPU time
>between DFT and DFTD is negligible.

>Kind regards,
>Alex Granovsky
>
>
>On Tue Oct 14 '14 4:27am, Siddheshwar Chopra wrote
>--------------------------------------------------
>>Dear Alex,
>>Thanks for the information. Do I need to preoptimize the sample? or should I just change the distance between graphene sheets and oprimize using DFTD?
>>Could you roughly estimate the cpu time difference between dft and dftd?

>>Kind Regards,

>>On Sun Oct 5 '14 7:44am, Siddheshwar Chopra wrote
>>-------------------------------------------------
>>>Dear Alex,
>>>Why DFTD? What is special about it? There are different versions of DFTD, so which onee would suit bilayer graphene work more?
>>>Kind Regards,

>>>On Sat Oct 4 '14 7:46pm, Alex Granovsky wrote
>>>---------------------------------------------
>>>>Hi,

>>>>as to bilayer graphene, perhaps the use of a good basis set together with DFTD could help.

>>>>Kind regards,
>>>>Alex Granovsky
>>>>
>>>>
>>>>On Tue Sep 30 '14 9:10pm, Siddheshwar Chopra wrote
>>>>--------------------------------------------------
>>>>>Dear Firefly users,
>>>>>I wish to work on twisted nanoribbons or bilayer graphene. But when I try to preoptimize it, the ribbon opens up and becomes planar, which is logical too. OR the bilayer graphene goes too far apart so that there is minimum interaction between two sheets.
>>>>>Somebody having experience with these samples, please suggest me how to go about these. Any tips related to Firefly regarding these samples will be welcomed.

>>>>>Kind Regards,

This message contains the 247 kb attachment
[ BG.out ] output file


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