Good afternoon again, I have a similar concern about lattice vectors: Based on the SIESTA tutorial link: http://dipc.ehu.es/frederiksen/tstutorial/index.php/Graphene <http://dipc.ehu.es/frederiksen/tstutorial/index.php/Graphene> Graphene - TStutorial<http://dipc.ehu.es/frederiksen/tstutorial/index.php/Graphene> In this exercise we use SIESTA/TranSIESTA to study an ideal sheet of graphene. We calculate the transmission curves as a function of (i) the k-point sampling and (ii) the size of the supercell. The procedures involves a number of steps: dipc.ehu.es the transmission increases (and thus the current) with the increase of ONE of the unit cell lattice vectors. My question is: Is this increase a linear relationship or not? In the tutorial increasing twice along the y axis lead to doubling of the transmission. Is that really the case GENERALLY? In other words if I double the unit cell along one direction, does that mean the transmission (and thus the current) will also double or not? Also what if we double the size on 2 different directions of the unit cell, does that lead to 4 times the transmission being larger or not? Thank you and looking forward to your reply.
El-abed Haidar | Doctor of Philosophy (Science) Condensed Matter Theory (CMT) Group | School of Physics THE UNIVERSITY OF SYDNEY | NSW | 2006 ________________________________ From: [email protected] <[email protected]> on behalf of El-abed Haidar <[email protected]> Sent: Saturday, 14 December 2019 9:08 AM To: Nick Papior <[email protected]>; siesta-l <[email protected]> Subject: Re: [SIESTA-L] TRANSIESTA QUESTIONs Concerning unit cell with skew lattice vectors Thank you again and really appreciate the content behind your answers. Even question one that i could not explain clearly you were able to answer that. Speaking of question one, you said that the electrodes would take care of the periodicity which is due to the electrode BLOCK TS.ELEC. Physically however i do not get how the electrodes can cover the other directions? I understand the reason which is that the electrodes and scattering regions must have the same OTHER DIRECTION LATTICE VECTORS. My concern is HOW? I tried to read the paper: Improvements on non-equilibrium and transport Green function techniques:The next-generation transiesta But i could not find that. Thank you ! EL-abed El-abed Haidar | Doctor of Philosophy (Science) Condensed Matter Theory (CMT) Group | School of Physics THE UNIVERSITY OF SYDNEY | NSW | 2006 ________________________________ From: [email protected] <[email protected]> on behalf of Nick Papior <[email protected]> Sent: Friday, 13 December 2019 8:01 PM To: siesta-l <[email protected]> Subject: Re: [SIESTA-L] TRANSIESTA QUESTIONs Concerning unit cell with skew lattice vectors Den tor. 12. dec. 2019 kl. 22.06 skrev El-abed Haidar <[email protected]<mailto:[email protected]>>: Thank you again for the reply For question 2 isn’t it defined as Ky and Kz so I’m not sure I get your point that it is fine I don't understand what you mean. :) A k-point is a k-point in Siesta AND in TranSiesta. However, there is no need for k-points along semi-infinite directions since the electrodes take care of the periodicity. For question 3 if our electrodes like our system are skewed ( direction of transport interested are a2 and a3) are we allowed to say a2 a3 ? If not what does a3 only mean for a skewed system? In other words how would transport take place in a skew system while specifying only one direction especially one would be mostly interested to cover You can't define transport to be aligned with 2 lattice vectors. You can ONLY define transport along a single lattice vector. But this lattice vector may have components along each of the 3 Cartesian directions. Thank you for your time really appreciate it El abed Sent from my iPhone On 12 Dec 2019, at 8:16 am, Nick Papior <[email protected]<mailto:[email protected]>> wrote: Den tir. 10. dec. 2019 kl. 22.04 skrev El-abed Haidar <[email protected]<mailto:[email protected]>>: Good evening I was just wondering if we have a unit cell with skew vectors ( c vector for example having y and z components) I have the following TRANSIESTA questions: This is only possible in 4.1 and beyond. 1- Based on siesta mail usually I usually define the k points as 1 1 100 Should I change it for skewed systems? I tried to look for the answer in the manual but it does not seem to give in depth on that. No, a lattice vector is still a lattice vector. So this should be fine. 2- May I know the difference between k points in a siesta run vs a transiesta run? I really want to know the in-depth understanding behind both. They both mean the same thing. However, in a transiesta run k-points along the semi-infinite direction has no meaning (the self-energies are semi-infinite by definition). 3- Which block in the siesta input file identifies the direction of the bias voltage ? Is there much more in depth to that? In 4.0 it is always the third lattice vector. In 4.1 it is determined from the semi-infinite directions of the electrodes. If they are parallel there exists a unique transport direction. Thank you and looking forward to all replies El abed Sent from my iPhone -- SIESTA is supported by the Spanish Research Agency (AEI) and by the European H2020 MaX Centre of Excellence (http://www.max-centre.eu/) -- Kind regards Nick -- SIESTA is supported by the Spanish Research Agency (AEI) and by the European H2020 MaX Centre of Excellence (http://www.max-centre.eu/) -- SIESTA is supported by the Spanish Research Agency (AEI) and by the European H2020 MaX Centre of Excellence (http://www.max-centre.eu/) -- Kind regards Nick
-- SIESTA is supported by the Spanish Research Agency (AEI) and by the European H2020 MaX Centre of Excellence (http://www.max-centre.eu/)
