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Topics - ams_nanolab

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136
General Questions and Answers / Contour plots for VB CB carrier densities
« on: January 17, 2013, 08:19 »
Dear Sir,

Is it possible to make contour plots of conduction band valleys as in

http://arxiv.org/pdf/1201.5284.pdf

http://www.sciencedirect.com/science/article/pii/S0038109812000889

with ATK?

137
General Questions and Answers / Error in effective mass calculation
« on: December 27, 2012, 12:45 »
Dear Sir,

I was evaluating the electron and hole effective masses in monolayer MoS2 using the effective mass analyzer. However I am finding some results to be quite surprising. The electron eff mass in the K-->Gamma direction is about 0.540 but the hole effective mass in the same direction is showing 2.002. The same trend is seen in other directions like K--> M etc. This is rather odd as the curvatures of the bottom CB and the top VB at K point seem quite similar from the bandstructure. Also a recent paper [http://prb.aps.org/abstract/PRB/v86/i24/e241401] on effective masses in monolayer MoS2 shows the electron and hole effective masses to be quite close for relaxed monolayer.

In our calculation we are following  the tutorial

http://quantumwise.com/publications/tutorials/mini-tutorials/135

and setting the value of Relative Band Index = 0 for electrons and -1 for holes.

Could you elaborate what is wrong?

138
General Questions and Answers / About the directions in the eff mass analyzer
« on: December 20, 2012, 13:56 »
I am looking to evaluate effective masses in a hexagonal system (graphene) at the K point in the K--> G and the K--> M directions. How to input that into the analyzer.

Also, is it okay to input fractional values like [1,1/sqrt(3),0] etc. into the direction box? or only [100], [010] etc. directions are allowed?

139
General Questions and Answers / Effective Mass Analyzer Hangs
« on: December 18, 2012, 15:15 »
When I'm using the effective mass analyzer, by dragging and dropping a NetCDF file in it, it seems to hang frequently. Say I'm performing calculations for a number of .nc files, after every 3rd or 4th file the analyzer hangs and vnl needs to be restarted again. I have tried with Auto Update disabled option but it still hangs after every 3rd-4th time.

I'm running ATK 12.8.0 on a RHEL server of good configuration, DFT calculations etc. finish quite well so I don't think teher's anything wrong with my hardware. The trouble is with the analyzer only. Is there a bug?

140
Installation and License Questions / Upgrade ATK
« on: December 11, 2012, 09:41 »
Is there a way to "upgrade" ATK from older versions to newer ones, presently I am making a clean install every-time a new version is released and then once again apply the plugins and so on. It would be nice if the installer could just upgrade the version keeping all the installed plugins and add-ons. ;D .

141
Installation and License Questions / Installing plugins in ATK 12.8
« on: December 10, 2012, 15:27 »
Dear Sir,

I recently installed ATK 12.8 in an RHEL server. I cannot install the buckle, twist etc. plugins as described in the thread http://quantumwise.com/forum/index.php?topic=1791.0#.UMXwRKxgWZQ

when I point to the zip file under Local Install and cotinue nothing happens.

Is the zip file OS/ ATK version dependent? Could u kindly give link for the right zip file for ATK 12.8 on Linux ?

142
General Questions and Answers / Applying strain in graphene
« on: December 10, 2012, 11:06 »
Dear Sir,

I was looking to apply strain to a graphene sheet. For this purpose I tried two methods:

1. Using the stretch cell utility in the builder, I applied strain to the graphene unit cell. However when I look to get the band diagram, the symmetry path G-M-K-G is no longer available, only G,Z are available. Thus it becomes difficult to understand the changes in band structure due to strain.

2. If I manipulate the Lattice parameters by small amount (say 10%) in the Bulk Tools to apply strain (keeping the Fractional co ordinates fixed of course), then it seems only the unit cell dimension increases and not the positions of the atoms within the cell. Also the band structures obtained do not seem to differ from the unstrained graphene.

Kindly suggest some solutions.

143
Installation and License Questions / Error
« on: December 5, 2012, 14:54 »
I recently installed ATK 12.8 on RHEL server.
I am getting the following error (screenshot attached)......

what is wrong?

144
General Questions and Answers / 12.8 release date?
« on: November 16, 2012, 08:51 »
Dear Sir,

When is the 12.8 release going to be available for download, and how to upgrade from the beta2 version to the official release?

145
Future Releases / Student standalone version
« on: November 9, 2012, 06:56 »
I was thinking why don't you launch a standalone student version of ATK at a reduced price? It could encourage more people especially in low-income / developing nations to use ATK.  ;D

146
Future Releases / MoSe2 in the materials database
« on: November 9, 2012, 06:50 »
Could you add MoSe2 in the database in the upcoming release?

147
General Questions and Answers / Rippled graphene sheet
« on: November 8, 2012, 11:56 »
Dear Sir,
If we want to twist / introduce ripples in a sheet of 2-D material, then how should we proceed?  For nanoribbon there are some codes/ plugins available here, but how to implement a rippled graphene sheet of say 10nmx10nm?

148
General Questions and Answers / HS.py
« on: November 8, 2012, 10:28 »
Dear Sir,

I am using the HS.py to obtain the system Hamiltonian as posted in http://quantumwise.com/forum/index.php?topic=1548.0#.UJt5gWffX1U

however the output i am getting is like

[[ -4.19645437e-02 -4.49943902e-18j  -2.38524478e-18 -7.39248005e-19j

    0.00000000e+00 +0.00000000e+00j  -2.42319186e-17 -6.11138787e-05j

    7.58941521e-19 +1.33195931e-18j   0.00000000e+00 +0.00000000e+00j

   -7.34151089e-02 -1.35525272e-19j   0.00000000e+00 +0.00000000e+00j

    4.78823195e-05 +9.48676901e-18j  -6.28841737e-05 +6.80929786e-17j

   -1.65869175e-01 -2.45004280e-17j  -3.27102739e-05 +4.53001691e-17j

   -4.74211396e-18 -1.65927479e-01j  -6.28841737e-05 +2.38863291e-18j

   -1.65869175e-01 -9.10475715e-18j   3.27102739e-05 -2.57286258e-18j

   -6.04315656e-18 -1.65927479e-01j]

...]

the fact that there's a space between the real and complex numbers

"a +ib"

instead of

"a+ib"

is making it difficult to read for other programs, could you kindly modify the HS.py script accordingly so it writes in a better format?


149
General Questions and Answers / Perturbed MoS2 monolayer
« on: November 3, 2012, 07:00 »
I am looking to find out the effect of perturbations like ripples, twists etc. of a monolayer MoS2 sheet on the system Hamiltonian. If ATK treats such rippled twisted sheets like a supercell, then does the symmetry points of the system changes from that of an unit cell? If so then how do we know the new symmetry points and their relation to the original(unperturbed) system?

150
Future Releases / MOSFET Simulation
« on: October 5, 2012, 12:40 »
Kindly add some plugins in the new version for simulating nano MOSFETs. If it could show output and trans-conductance characteristics it would be just great :)

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