Messages

76

General Questions and Answers / Re: system cannot be transformed to device configuration

« on: May 13, 2011, 05:18 »

Well....I have another question....

Do we only need to add iteration_control_parameters = NonSelfconsistent to the Device Calculator to make the device calculation a non-scf one, without specifying other optimization-related parameter, such as atomic constrants? The programme will automatically add constrain to the electrode copy region, right?

Is the script attached right for geometry relaxation?

Thanks! (*^__________^*)

baizq

77

General Questions and Answers / Re: system cannot be transformed to device configuration

« on: May 12, 2011, 17:13 »

Hi Anders,

Thanks very much for your reply, especially for the trick provided I am going to make a try.

baizq

78

General Questions and Answers / Re: system cannot be transformed to device configuration

« on: May 12, 2011, 14:55 »

1. It seems that VNL cannot recognize the electrode length after geometrically optimizing the Fe-MgO-Fe structure as bulk configuration. As a result, it cannot convert the bulk configuration back to device and then exhibit the above error message. Anyone who knows how to deal with the problem?

2. Or other than relaxing the structure as bulk configuration as recommended by the tutorial, can we optimize it as device configuration? If we can, how to set the K-point grid and other main parameters?

3. It is said in the tutorial that geometry optimization as bulk configuration can speed up the computation. Why...?

79

General Questions and Answers / Re: How to set the spins of the right and left electrode atoms respectively?

« on: May 11, 2011, 17:41 »

This requires a rather long explanation, however maybe you can just have a look in the upgrade guide. I hope that answers your question

good answer...thanks....

80

General Questions and Answers / Re: Calculation the transport properties of graphene

« on: May 11, 2011, 14:58 »

but the properies look like nanoribbon, with quantized transmission spectrum

I guess that your transmission spectrum is step-like but the values are not integer.
Is this right?
If so, your calculation is reasonable, graphene should have such a feature.

I think over 50 angstroms is too long and you can reduce the size along z direction to 7-10 angstroms.
(Maybe even the primitive cell size is OK, I'm not sure because I don't know the detailed algorithm though...)

Hi nori,

Thanks for your reply...
Actually this question is posted by my labmate...Actually I even do not know what bulk graphene is.... Actually he has gone to Malaysia...Actually we can neglect this question...
Anyway...Thanks very much !!

baizq

81

General Questions and Answers / Re: How to set the spins of the right and left electrode atoms respectively?

« on: May 11, 2011, 13:07 »

Actually you don't set the spin of the electrodes in 11.2, you set it on the electrode copy regions in the central region, and ATK copies these initial spins to the electrodes.

The tutorial on FeMgO should explain it all!

Hi Anders,

Why are there electrode copy regions in the central region in ATK 11.2?

Suppose I want to set up a Fe-MgO-Fe MTJ device with 6 MgO barrier layers and 4 Fe electrode layers, as well as 2 Fe surface layers, as what is recommended in the tutorial. Why does the appearance in device mode looks like we have another 4 Fe layers at each side of the device? They are called electrode copy regions as you mentioned,right? Then when we want to calculate transport properties of the system, how many Fe layers are really taken into consideration by the algorithm?

thanks!
baizq

82

General Questions and Answers / system cannot be transformed to device configuration

« on: May 11, 2011, 11:18 »

Dear Colleagues,

I am following one tutorial of atk 11.2 : Spin transport in MTJ Fe-MgO-Fe, and encountered with an error as followed:

Error: the total width of the left and right electrodes may not exceed the width of the central region.

when I want to tranform the structure  from bulk configuration back to device configuration after geometry optimization.

Anyone knows what the problem is and how to solve it?

Thanks,
baizq

83

General Questions and Answers / Calculation the transport properties of graphene

« on: May 4, 2011, 16:38 »

Dear all,

is the anyone who has done calculation of the transport properties of bulk graphene using ATK? I have tried by using bulk graphene as electrode and bulk graphene(over 50 angstroms in the transport direction), but the properies look like nanoribbon, with quantized transmission spectrum. The IV curve is linear, which I think it is wrong. Is this because I use less kpoints or something wrong with setting?

help,help..............

84

General Questions and Answers / Re: LDA+U for transport calculation

« on: April 22, 2011, 15:45 »

Can we apply LDA+U (or GGA+U..or whatever+U) to transport calculation?

Yes
One example is attached, which mimics the calculation presented in Appl. Phys. Lett. 94, 252103 (2009).

Hi nori,

Nice to see you back. Thanks a lot for your kind reply. 

baizq

85

General Questions and Answers / LDA+U for transport calculation

« on: April 22, 2011, 09:48 »

Dear colleagues,

Can we apply LDA+U (or GGA+U..or whatever+U) to transport calculation?

Thanks,
baizq

86

General Questions and Answers / SOI and spin-dependent voltage drop

« on: April 20, 2011, 04:32 »

Dear colleagues,

I have two questions:

1. Is spin-orbit interation taken into consideration by atk when we conduct a two-probe transmission calculation;

and

2. Can we calculate spin-resolved voltage-drop with ATK 11.2?

Thanks,
baizq

87

General Questions and Answers / iv calculation with ATK 11.2

« on: April 8, 2011, 14:29 »

Dear colleagues,

Is there anybody who knows how to calculate iv characteristics of a two-probe device with the new version ATK 11.2? Do we need a seperate script?

Thanks.
baizq

88

Installation and License Questions / Re: trouble in starting VNL

« on: March 14, 2011, 14:21 »

Yes, the motherboard graphical card is activated. It is said that VNL 10.8 cannot start without a external graphical card but VNL 11.2 has removed the bug...right?

89

Installation and License Questions / Re: trouble in starting VNL

« on: March 14, 2011, 11:31 »

The system in our machine is OPENSUSE 11.3 X64.
The previous version of VNL (10. cannot work on our machine either. But that may be due to graphical card reason because the ATI graphical card is not activated on the machine....
VNL 08.10 can be used in the machine.

90

Installation and License Questions / Re: trouble in starting VNL

« on: March 14, 2011, 09:16 »

Yes...Actually there are 3 versions of ATK on that machine..... 08.10, 10.8 and 11.2
Do I have to delete the old versions..?