Topics

1

General Questions and Answers / Transmission and its relation on Current

« on: September 5, 2011, 12:30 »

Hi

Is current anyay related to the values of transmission. like if it is directly proportional to value of transmission??

i measured the current carried by a small AGNR for different potential biases and plotted its transmission spectrum

then i removed an atom from the AGNR and then plotted its transmission spectrum

though the value of transmission had decreased in the second case, the current conducted at certain potential biases is like 8 times the current carried by the defectless structure.

can this thing be right??

i have attached the images of AGNR's i used

regards
deepak

2

General Questions and Answers / A clarification about IV characteristics

« on: August 19, 2011, 14:18 »

Hi

i had formed a small AGNR with m=0, n=5 and z axis repetition 4 and calculated its current at 1.5 V bias and removed an atom from the center of the structure and calculated its current at 1.5V. I was hoping that current in the defectless structure would be high. But it turned out that current in structure in which an atom was missing was high (all other parameters were same and both structures were optimized using Brenner potential method). can anybody if this is correct or i am doing any mistake while forming the structures, please/ i have attached both the structures with this mail.

3

General Questions and Answers / small clarifications about electrodes

« on: August 13, 2011, 20:00 »

hi

i had created this structure (removed a couple of layers of carbon atoms and used passivate script) but now i am not able to attach electrodes to it

it shows an error "Total width of electrodes may not exceed width of central region"
can you please what is this error about and how to rectify this. i want to attach electrodes to the same structure. i have faced this error a lot times before as well and i dont know when exactly this comes as sometimes i am able to attach electrodes to constricted GNRs

regards
deepak

4

General Questions and Answers / a small doubt in TranSIESTA

« on: August 11, 2011, 12:21 »

Hi

sorry for starting it here but since i could not get help anywhere else about it i thought of asking it here as VNL is also based on SIESTA/TranSIESTA


ts_iohs: BAD DIMENSIONS
and then run terminates

what is this error
it comes just after it starts to read the left electrode dimensions

i found that a file called ts_iohs.h is generated

it contains:

C Dimensions for input to ts_iohs
   parameter (nspin = 1499993)


i checked the buffer atoms no and all and it seems right

what exactly is this TSiohs (i found files going by that name in TBTrans directory)

please help
deepak

5

General Questions and Answers / Error while optimizing a structure

« on: July 29, 2011, 19:09 »

Hi

I tried to optimize a structure of ZGNR with some structural defects , it becomes a haphazard structure within first few run only and continues to deteriorate . please someone tell what is wrong with my structure. I followed the procedure given in tutorials for optimization

regards
deepak

6

General Questions and Answers / Three Electrode Configuration

« on: July 16, 2011, 18:15 »

Hi

Is it possible to create a structure that contains a three electrode configuration
does ATK support that type of calculation

7

Installation and License Questions / Trouble opening Latest VNL in XP

« on: June 22, 2011, 11:04 »

Hi

My friend had installed the latest VNL (32 bit - windows version) in his comp running XP using a trial license valid till 30th June. When he tries to open it for the it shows the following error

License Error: (Internal :262 ...)

Err 18: System Clock has been set back


i searched the forum and could not get any help
how to correct this

regards
deepak

8

General Questions and Answers / Trouble while plotting Bandstructure

« on: June 16, 2011, 12:30 »

Hi

i tried to plot bandstructure for a carbon nanoribbon structure
when i use print option there are values shown in the log

but when i try to view it nothing is shown
can anyone explain why??

i face similar problem in Analyzer

whenever i maximise the window the plot which was there before cannot be seen

regards
deepak

9

General Questions and Answers / Eigenvalue vs Electric Field Plot

« on: March 2, 2011, 04:56 »

Hi

I had been going through a certain simulation thesis where they had plotted Eigenvalue vs Electric Field plot for a hydrogen terminated silicon double quantum dot structure
i just tried to do it by running different simulations for different values of electric field but with different values of electric field we have different fermi energy and i dont know how to integrate these values and make a unified plot
Can anyone please help

10

General Questions and Answers / Problem while trying to find conductance

« on: January 11, 2011, 06:34 »

Hi
i used this piece of code from tutorials to plot conductance

# Read first transmission spectrum from file struct1.nc
transmission_spectrum = nlread("/root/Desktop/Run1/struct1.nc",TransmissionSpectrum)[0]
#make list of temperatures
temperature_list=numpy.linspace(0,2000,21)*Kelvin
#make list for holding conductance
conductance_list=numpy.zeros(len(temperature_list))
#calculate the conductance for each temperature in the temperature list
for i in range(len(temperature_list)):
    conductance_list=transmission_spectrum.conductance(
         electrode_temperatures=(temperature_list,temperature_list) )
#plot the conductance as function of temperature
import pylab
pylab.figure()
pylab.semilogy(temperature_list,conductance_list)
pylab.xlabel("Temperature (K)")                                   
pylab.ylabel("Conductance (S)")
pylab.show()


but i am getting this error
ImportError: libstdc++.so.5: cannot open shared object file: No such file or directory

i tried creating symbolic link
ln -s /usr/lib/libstdc++.so.6 libstdc++.so.6

but still the problem exists
is libstdc++.so.5 different from libstdc++.so.6
how to make it use libstdc++.so.6

11

Installation and License Questions / Trouble installing ATK 64 bit linux version

« on: January 5, 2011, 07:44 »

hi

when i launch the binary file of 64 bit version of atk in a linux system it says permission denied
on googling i found some SELinux systems may not allow to launch the software after installing it
however i am not able to install the software itself
i am using debian 5.0 with 6GB ram
my computer meets all the system requirements
also 32 bit version installs without any problem

kindly help

12

General Questions and Answers / Runtime terminated in unusual way

« on: January 4, 2011, 19:02 »

hi

i am getting the error following error for a device structure


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

i an old thread some one had said lack of memory might be a reason (sorry for creating a new thread)
however i am getting the same error in a linux system with 6 GB memory
kindly help

regards
deepak

13

General Questions and Answers / Long int too large to convert to int

« on: December 8, 2010, 11:49 »

Hi when i was trying to calculate Density of States for an armchair GNR
i get this error

Traceback (most recent call last):
  File "/tmp/4171684607458975.py", line 347, in <module>
    nlsave('analysis.nc', bulk_configuration)
  File "./zipdir/NL/IO/NLSaveUtilities.py", line 212, in nlsave
  File "./zipdir/NL/IO/NetCDFFile.py", line 170, in close

Timing:                          Total     Per Step        %

--------------------------------------------------------------------------------

Diagonalization         :     477.41 s      36.72 s      82.19% |========================================|
Real Space Density      :       6.89 s       0.49 s       1.19% ||
Hartree Potential       :       1.25 s       0.09 s       0.22% |
Mixing                  :       0.00 s       0.00 s       0.00% |
Laplace Kernel          :       0.00 s       0.00 s       0.00% |
--------------------------------------------------------------------------------
Total                   :     580.83 s (9m40.83s)
  File "./zipdir/NL/IO/NetCDFFile.py", line 194, in flush
  File "./zipdir/NL/IO/NetCDFFile.py", line 207, in _write
  File "./zipdir/NL/IO/NetCDFFile.py", line 267, in _write_var_array
  File "./zipdir/NL/IO/NetCDFFile.py", line 310, in _write_var_data
  File "./zipdir/NL/IO/NetCDFFile.py", line 518, in _pack_begin
  File "./zipdir/NL/IO/NetCDFFile.py", line 523, in _pack_int
OverflowError: long int too large to convert to int
NanoLanguageScript execution failure

how to rectify this

14

General Questions and Answers / Finding BandGap

« on: November 23, 2010, 16:46 »

hi

i am new to this forum
can anyone please tell me how to find bandgap/bandstructure of a graphene nanoribbon
i followed the tutorial but bandstructure option is not there in analysis function
also i dont know how to access the eigen values that are computed during the run as band gap can be found from there using homo and lumo values

regards
deepak