QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: Sumit2506 on December 17, 2013, 07:09

Title: Error message
Post by: Sumit2506 on December 17, 2013, 07:09: Sir,
When I am calculating the Phonon Bandstructure of Carbon nano tube with near about 80 atoms,
I is always getting failed and showing the message some thing like "VNL has terminated in unusual way "
Please suggest me what should i do .....

With highest regard
Title: Re: Error message
Post by: zh on December 17, 2013, 07:46: The job may be too heavy for your computer resource and it runs out of your memory.

If you use the primitive unit cell of periodic CNT, you can reduce the number of atoms in your simulations.
Title: Re: Error message
Post by: Anders Blom on December 17, 2013, 11:44: See the tutorial (http://quantumwise.com/documents/tutorials/latest/Phonon), and try reducing the number of repetitions in the C direction.
Title: Re: Error message
Post by: Horen on December 18, 2013, 03:38: Quote from: Anders Blom on December 17, 2013, 11:44
See the tutorial (http://quantumwise.com/documents/tutorials/latest/Phonon), and try reducing the number of repetitions in the C direction.

I have the same problem,and Ialso see the tutorial,but I still do not know how to do.
Title: Error message
Post by: Sumit2506 on December 18, 2013, 07:59: Sir,
I have reduced the repetition and run it with minimum no. of atoms possible, but it is again showing the same error message "The application has requested the run time to terminate it in unusual way .Please contact the application support team for more information", can You suggest me the minimum memory requirement for calculation of these properties with structure having the atoms near about 100.

With Highest Regard
Title: Re: Error message
Post by: Anders Blom on December 18, 2013, 09:32: One should be aware that phonon calculations are heavy lifting. On the other hand, ok 100 atoms - but what method? With the Tersoff potential I can do a phonon spectrum calculation of a (5,5) CNT with a Stone-Wales defect (200 atoms in total) in under 2 minutes on my laptop. The calculation uses about 120 MB of memory.

But a phonon calculation with 100 atoms with DFT, it might need 2 or 8 or 16 GB or more, it's impossible to tell without knowing the details of the system.
Title: Re: Error message
Post by: Sumit2506 on December 19, 2013, 06:15: I am calculating the Phonon bandstructure of (5, 5) CNT with 4 repetition in Z direction ,Using my system which is having i7 processor and 2 GB ram
Title: Re: Error message
Post by: Anders Blom on December 19, 2013, 09:46: 2 GB is too little to do anything serious with DFT.