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Messages - PR

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1
General Questions and Answers / Nanowire with specific transport and side wall orientations
« on: February 21, 2016, 06:36 »
Dear sir,
I want to make a silicon nanowire with transport in [110] direction and side walls along (1 -1 0) and (001) direction.  Can someone tell me the steps, how I can get the specified combination in VNL.

2
General Questions and Answers / Re: Discrepency in Effective mass calculation
« on: May 31, 2015, 10:18 »
I have again calculated the effective mass values for X valley in [101]  direction for ml and getting value of ml = 52.0858 and in [010] for mt= 0.375864.
Here ml is again questionable. It would be helpful if anyone can tell me now where I am doing wrong for ml calculation.


Thanks
PR

3
General Questions and Answers / Re: Discrepency in Effective mass calculation
« on: May 29, 2015, 18:48 »
================================
For the X valley of bulk InAs:
values obtained using ATK: ml=mt=0.37, the value doesn't change on changing the direction ([010] for ml and directions perpendicular to it for mt), suggesting a isotropic mass, which is wrong!
This is also in contrast with the data (target values: mt=0.23, ml=1.3) in the reference cited in your reply (Boykin et. al, PRB 2002).
Could you please calculate at your end let me know the values you are getting?

Thanks.

4
General Questions and Answers / Re: Discrepency in Effective mass calculation
« on: May 29, 2015, 17:41 »
Thank you all for your replies.
@ Admin, I have not tried for other basis sets, but as suggested by Jess Wellendorff, I will try FHI DZP and OMX tier basis sets.


Regards
PR.

5
General Questions and Answers / Discrepency in Effective mass calculation
« on: May 28, 2015, 10:50 »
Hello,
I am calculating the effective mass (ml and mt) for InAs bulk in Gamma and L valleys, using both of the two methods given in ATK 2014.2 version. The values in Gamma valley is quite close to the literature [1], but for L valley there is a discrepency in values.
Direction used :  [111] for ml and [-110] for mt for L valley.
Methods for effective mass calculation:
(1) Effective mass analyzer under tools tab is giving  ml = 1.827  and mt=0.121.
(2) Effective mass calculating directly from plugin given at bottom right corner in the band structure plot window is giving  ml=0.609 and mt=0.305.
While the values are ml = 0.64 and mt = 0.05  in literature [1]

Can you please tell me why the tool is giving different results with different effetive mass analyzers and which one is more reliable.
Also, why the values are not consistent with literatre. Where I am doing mistake or what  should I change to get the correct results.
Attaching the python script of the calculations.
Reference:
[1] I. Vurgaftman, J. R. Meyer and L. R. Ram-Mohan "Band parameters for III–V compound semiconductors and their alloys" J. Appl. Phys. 89 5815 (2001)

6
General Questions and Answers / Effective mass direction
« on: May 15, 2015, 07:41 »
Dear sir,
In bulk silicon, the direction from Gamma to X is (100) as per the existing literature and also as per the NSM archive link:
http://www.ioffe.ru/SVA/NSM/Semicond/Si/Figs/121.gif

But according to your tutorial on silicon effective mass, given on link :
http://quantumwise.com/publications/tutorials/item/500-effective-mass-of-electrons-in-silicon

this direction is (101). Can you please clarify why it is not matching with the literature.



Regards
PR

7
General Questions and Answers / Re: Polarization result mismatch in BaTiO3 crystal
« on: February 19, 2015, 11:20 »
I didn't get you. I think you are talking about Ionic fractional polarization, while my question is about Total fractional polarization.
Again attaching the snapshot. Please see the highlighted part only and compare the powers (-15 and -16) with your tutorial.
 

8
General Questions and Answers / Re: Polarization result mismatch in BaTiO3 crystal
« on: February 19, 2015, 07:55 »
Thanks for the reply.
The numbers are not same. If you see carefully, I am getting the order of -15 instead of -16 in Total Fractional Polarization second row. 
Can you please explain the reason (if possible). And how can I get the same results as in tutorial.

Thanks

9
General Questions and Answers / Polarization result mismatch in BaTiO3 crystal
« on: February 18, 2015, 11:08 »
Hi all,
I am trying to reproduce the results of polarization in BaTiO3 using ATK 2014.2 version, as given in your tutorial at link :
http://quantumwise.com/documents/tutorials/latest/Polarization/index.html/chap.batio3.html#sect1.batio3.structure
I am following all the steps as mentioned in tutorial, but getting different values from tutorial result.
Attaching the snapshots of calculation and results which I am getting.
Can somebody tell me the reason for this discrepancy?
What should I do to get the correct results.

10
General Questions and Answers / No option visible for random alloy in ATK 2014.2 version
« on: January 28, 2015, 09:43 »
Hi,
I am trying to reproduce your tutorial for band structure on random alloys given at below mentioned link in the latest ATK version 2014.2, but I am unable to find any option of substitutional alloy inside builder:
http://quantumwise.com/publications/tutorials/item/850-effective-bandstructure-of-random-alloy-ingaas.
Attaching the snapshot of the options visible to me.
What could be the possible reason and solution for that.

11
General Questions and Answers / Rhenium DiSulphide structure
« on: January 5, 2015, 13:02 »
Hi,
I am trying to make ReS2 structure via crystal builder, as mentioned in the paper "Monolayer behaviour in bulk ReS2 due to electronic and vibrational decoupling" by Sefaattin Tongay et. al.
But I am not getting the exact structure as mentioned in paper. Can you please explain how can I make it or can you provide the python script for that.


Thanks
PR.

12
General Questions and Answers / Ensemble DFT in ATK 2013.8.1 ?
« on: December 18, 2014, 05:04 »
Hello,
I am doing some simulations using DFT LDA for crystal geometry optimization and bandstructure calculation at 300K temperature in ATk 2013.8.1.
My question is that when we say the simulation is done at 300k, does it mean that ATk is using ensemble DFT method for geometry optimization.



Thanks
PR

13
General Questions and Answers / Re: How to obtain the electron matrix elements of the Hamiltonian and overlap?
« on: September 30, 2014, 08:27 »
Hello,
I am using ATK 2014 version.
Can you please tell me how can I extract these matrix elements, Hamiltonian and overlapping, from GUI.
If not directly from GUI then can you please provide some script for the same.



Thanks
PR.

14
General Questions and Answers / Re: Tight Binding Parameter extraction
« on: September 26, 2014, 07:03 »
Isn't there any possible way to get these parameters directly from ATK?

15
General Questions and Answers / Tight Binding Parameter extraction
« on: September 23, 2014, 06:49 »
Hello Sir,
I want to extract tight binding parameters for some geometry in ATK 13.8.1 version.
Can you please tell me the steps (or code) to extract those parameters.


Thanks
Priyank

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