Messages

91

Installation and License Questions / Re: trouble in starting VNL

« on: March 14, 2011, 04:25 »

  Actually I am running on the workstation where ATK&VNL are installed
I have followed all the steps in the installation guide. It is quite strange that ATK command line mode can be used but VNL cannot....

92

Installation and License Questions / Re: trouble in starting VNL

« on: March 13, 2011, 08:48 »

Hi Anders,

I have tried type vnl in the command line, and it is shown like followed:

z400workstation@160-218:~/QuantumWise/atk-11.2.0/vnl/bin> vnl

_IceTransSocketUNIXConnect: Cannot connect to non-local host linux-uflo
_IceTransSocketUNIXConnect: Cannot connect to non-local host linux-uflo
Qt: Session management error: Could not open network socket
/home/z400workstation/QuantumWise/atk-11.2.0/vnl/bin/vnl: line 3: 13450 Segmentation fault      VNL_PATH=$EXEC_DIR/../.. PSEUDOPOTENTIALS_PATH=$EXEC_DIR/../../atkpython/share/pseudopotentials PYTHONHOME=$EXEC_DIR/.. PYTHONPATH= LD_LIBRARY_PATH=$EXEC_DIR/../lib $EXEC_DIR/vnl_exec $*

So what does it mean.....

Thanks!
baizq

93

Installation and License Questions / trouble in starting VNL

« on: March 12, 2011, 13:44 »

Dear all,

I have installed ATK 11.2 combined with VNL, and loaded a trial license for OPENSUSE 11.3 Linux x64 system. I have found that it is ok for atk command-line mode, but when I want to use the graphical interface, VNL cannot be started. It does not give any error information either, just no response.

So what is the problem? Is it necessary to activate the ATI graphical card in our workstation, instead of using the default one of the system, to run VNL?

Thanks.
baizq

94

General Questions and Answers / Re: Convergence problem of Heusler alloy

« on: March 8, 2011, 03:02 »

Hi nori,

Thanks very much for your scripts and suggestion.

I will try ATK 10.8.

baizq

95

General Questions and Answers / Re: Convergence problem of Heusler alloy

« on: March 7, 2011, 08:31 »

Dear nori,

I have another two questions...

How to do a bulk calculation to find the spin value as initial guess...

And will the initial spin converge to the correct spin configuation after self-consistent iterations? For example, the central spacer Cu2CrAl is a non-magnetic material. Can we get it as non-magnetic after setting a initial spin and conducting scf run?

Thanks very much. (*^___^*)
baizq

96

General Questions and Answers / how to treat lattice mismatch of a GMR junction

« on: March 7, 2011, 08:21 »

Dear colleagues,

How to treat the GMR junctions, of which the electrode and space layer have a lattice mismatch?

For example, in Co/Cu/Co spin valve, the lattice constant of fcc Cu is 3.615A, whereas it is 3.5447A for fcc Co. There is around 2% lattice mismatch. How should we deal with this? It is correct to compress the lattice constant of Cu spacer to the same value as Co (force Cu lattice constanct to be 3.5447A)? Will this method lead to large error?
Or should we conduct a relaxation first to determine all geometry factors of the system, such as the lattice constancts of both spacer and eletrode, the distance between the last screening layer and the first space layer, and so on....

Thanks
baizq

97

General Questions and Answers / Re: Number of kpoints needed for GMR structures

« on: February 24, 2011, 14:39 »

Dear Blom,

Thanks for your rapid reply.

Actually I have found a tutorial on ATK website called 'Modeling of magnetic tunnel junctions', in which on the last page it shows an IV curve for Co/Cu/Co GMR spin valve. I just would like to know how you set the kpoints for that case, or would you please suggest a kpoint mesh size as a starting guess?

Besides, as you say, how to analyze the k-point dependent tranmission coefficient..could you please state it a little more specifically...

baizq

98

General Questions and Answers / Number of kpoints needed for GMR structures

« on: February 24, 2011, 13:44 »

Dear colleagues,

I am now working on the transmission properties of GMR junctions. I have found in ATK manual(version 2008.10) that, for TMR structure Fe/MgO/Fe, it is always necessary to include large number of kpoints for transmission spectrum calculation (k-mesh 301x301 as in the tutorial).

Here is my question : what about GMR structures, say, Co/Cu/Co , or Co2MnSi/Ag/Co2MnSi which has demostrated the largest MR ratio experimentally?  Approximately how many kpoints are needed for such systems when calculating transmission spectrum or IV curve?

Manny thanks.

baizq

99

General Questions and Answers / Re: Convergence problem of Heusler alloy

« on: February 20, 2011, 07:23 »

Dear nori,

Many many thanks for your help.

I have tried the script for antiparallel case. It converges after 56 loops. Really appreciate your help. 

baizq

100

General Questions and Answers / Re: Convergence problem of Heusler alloy

« on: February 12, 2011, 06:16 »

Dear nori,

Thanks for your help with our problem. I have tried your script and convergenve is really achieved after 23 loops. I have to say that your modified script is a great support to our work because we struggled to tune the parameters but the system was always failing to converge.

I also have a question here: why do you set the initial elemental spins as those in your script? How did you determine the values, such as 1.0 for Cr, 0.1 for Co, -0.13 for Si and so on? Since after convergence, I have to calculate the transmission properties for both antiparallel and parallel cases, and I have no idea how to set the initial spins for each kind of element involved, could you please kindly give me some suggestion on this issue?

Thanks!
baizq