Messages

91

Scripts, Tutorials and Applications / Re: An Error for calculating the current of LiH2 chain

« on: March 28, 2010, 11:31 »

Probably your problem can be solved by changing the script as follows:
before)
transmission_spectrum = nlread("LiH2.nc",Transmission Spectrum)
after)
transmission_spectrum = nlread("LiH2.nc",TransmissionSpectrum)[0]


Please note that an index starts from not "1" but "0" in Python.
I guess there is only one Transmission data in your "LiH2.nc" and that's why you got the error message "IndexError: list index out of range" in the first calculation.

92

General Questions and Answers / Re: spin-polarized transport calculation with magnetic electrodes

« on: March 25, 2010, 09:59 »

I think electrode_constraint is the main cause of unstable SCF in your calculation.
If you select "ElectrodeConstraints.RealSpaceDensity" instead of "ElectrodeConstraints.Off", the SCF convergence will be dramatically improved.
I've verified it with "111niben_2.py".
In "111niben_2.py", several other parameters are changed but probably these changes are trivial but only "ElectrodeConstraints.RealSpaceDensity" is indispensable for solving this issue.

93

General Questions and Answers / Re: IV-Voltage Drop

« on: March 5, 2010, 07:42 »

Your voltage drop seems alright at least computationally.
(I don't know this result is right physically though...)

I guess the current flow is from left to right(electron flow is from right to left) and the value of current is quite small.
Is this right?
In ATK, non-equilibrium density matrix is included in finite bias calculation, which may be important to understand your voltage drop.
At left electrode, there is almost no transmitted electron because of high resistance of SiO2, so that the electronic structure doesn't change
from equilibrium one.
On the other hand, at right electrode, the electronic structure could be dramatically changed from equilibrium one because there are incident electron and reflected electron.

If you want to obtain a voltage drop more smoothly connected to reservoir at right electrode, it may be good prescription to increase surface layers of right electrode.

94

General Questions and Answers / Re: Why scf calculation for a two probe system only converge for the SZ basis se

« on: January 21, 2010, 04:09 »

According to "scf.out", SCF calculation seems to be converged with more dozens of iterations.
But unfortunately converged density matrix will be unphysical because of electron reduction in the whole system.
The system has 275 electrons as neutral, on the other hand, SCF calculation goes toward the state that loses 32 electrons.

It's probably due to "electrode_constraint".
If you use "ElectrodeConstraints.Off", I recommend that you use "ElectrodeConstraints.RealSpaceDensity" instead of it.

95

General Questions and Answers / Re: the current calculation of the python script

« on: November 22, 2009, 10:22 »

Perhaps you can make it by modifying 4th line of "current.py" as follows:
(before)
transmission_spectrum = nlread("/home/zjl/JOB/Si_0_0.nc",TransmissionSpectrum)[1]
(after)
transmission_spectrum = nlread("/home/zjl/JOB/Si_0_0.nc",TransmissionSpectrum)[0]

Please note that list index starts from not 1 but 0 in Python.

96

General Questions and Answers / Re: Can anyone tell me is the calculated results right or not?

« on: November 20, 2009, 15:32 »

Your calculation result means that transmission coefficients around fermi level are not zero but less than 5e-5.
I recommend that you use the method in ATK manual in order to get more precise transmission spectrum.

http://www.quantumwise.com/documents/manuals/ATK-2008.10/ref.calculatetransmissionspectrum.html

By the way,
>333 Li     q =  1.88239 [ s:  0.787, py:  0.276, pz:  0.549, px:  0.271 ]
>334 Li     q =  1.59546 [ s:  0.685, py:  0.248, pz:  0.419, px:  0.243 ]
>335 Li     q =  1.86874 [ s:  0.785, py:  0.273, pz:  0.543, px:  0.267 ]

I feel that the mulliken population of Li elements is strange because it should be around 1.
In my experience, I sometimes get unphysical mulliken population with ElectrodeConstraints.Off.
Then using "ElectrodeConstraints.RealSpaceDensity" can resolve the issue.

97

General Questions and Answers / Re: Why can not I bulid a supercell like this?

« on: November 18, 2009, 06:38 »

You should write the python code like "a.py".
"Indentation" part of Python basics in ATK 2008.10 manual will help your understanding.

http://www.quantumwise.com/documents/manuals/ATK-2008.10/chap.pythonbas.html#sect1.pythonbas.indent

98

General Questions and Answers / Re: A countour plot is failed in VNL 2009.06.2

« on: September 17, 2009, 04:41 »

This might, in some cases, require a kernel update,

That's right.
It's known that default kernel of OpenSUSE 11.1 has several problem, that's why at first I failed to install Nvidia driver for OpenSUSE.
This problem is refered in several site.
I could install Nvidia driver by updating kernel. Now I can obtain contour plots in VNL 2009.06.2.

Thanks for your help!

99

General Questions and Answers / A countour plot is failed in VNL 2009.06.2

« on: September 3, 2009, 09:15 »

Dear QuantumWise Staff,

I've found that there is probably a bug with displaying a contour plot in VNL 2009.06.2.
When I tried to view the effective potential of GNR 2probe with contour plot, I obtained one line like attached.
In addition, even one line is disappeared if any parameter for plot is altered.

My OS is OpenSUSE 11.1 for 64-bit.
Is this problem specific for OpenSuse?
Is there a way to avoid this problem with some tips in VNL 2009.06.2?

Thanks in advace.

100

General Questions and Answers / Re: how to explain this? is it wrong?

« on: August 27, 2009, 07:05 »

Could you give us the scripts for both SCF and PDOS?

101

General Questions and Answers / Re: how to explain this? is it wrong?

« on: August 26, 2009, 17:30 »

I strongly recommend that you should calculate the pdos, which is the dos projected on the molecule in the central region of your 2-probe system.
from the pdos, you would be able to realize the relationship between the transmission and the electron state of central region

In most cases, a pdos is more useful for analyzing　physical properties than a dos.
(at least, I believe it !)

102

Installation and License Questions / Re: about a port for new license system

« on: August 18, 2009, 10:33 »

>So, in practice, the port cannot be changed (for that, we would have to rebuild the entire license library).

I got it, thanks.


>However, I don't really see any reason why the port would need to be changed

Actually, this question is from our customer.
Many applications are installed in their computational system and also many ports are alreadly used for each application.
That's why they want to know which ports is used and how to change a port in order to set up ATK-SE safely.

Is it possible to rebuild the entire license library if port 5093 is already used for other application and customers need defferent port?

103

Installation and License Questions / Re: about a port for new license system

« on: August 18, 2009, 02:19 »

Hi Anders,

Thank you for your reply.
According to the web site, "although this(= port 5093) can easily be changed to an alternative. ",
but I couldn't find out the way.

Could you tell me how to change a port from default?

104

Installation and License Questions / about a port for new license system

« on: August 17, 2009, 11:39 »

Dear QuantumWise support staff,

I'd like to know which ports is used for new license system and how to change a port.
New license system means a license system offered by Safenet.

Thanks in advance.

105

General Questions and Answers / Re: Can a numerical data of transmission spectrum in a VNL file be extracted?

« on: July 6, 2009, 11:36 »

Dear zh,

Thank you so much for your perfect answer!!!