Dear Adel, It seems that you did not get it correctly. A hopping is a tuple of two sites which make a bond in your lattice. So the direction is not important.
Hop=(site1,site2) Hop[0]=site1 Hop[1]=site2 I suggest to you to have a look at the frequently asked questions in kwant [1]. It explains a lot of interesting things. I hope this helps. Regards, Adel [1] https://kwant-project.org/doc/1/tutorial/faq On Mon, Sep 9, 2019 at 2:15 PM Adel Belayadi <[email protected]> wrote: > Dear Joseph. > Thank you for your reply. If I got it well, you mean the first site the > hopping along x direction and second site the hopping in the y direction. > Best > A.BELAYADI > > Le lun. 2 sept. 2019 à 09:15, Joseph Weston <[email protected]> a > écrit : > >> Hello, >> >> >> What is the difference between hop[0].tag and hop[1].tag >> >> hop[0].tag is the tag of the first site in the hopping and hop[1].tag is >> the tag of the second site in the hopping. >> >> >> >> My second question >> the onsite fuction for example: def onsite(site, V):return V >> >> why it depends on site where the shape functions for example >> def circle(pos): rsq = pos[0] ** 2 + pos[1] ** 2 >> depends on pos >> >> Because when creating a shape in realspace you typically only care about >> the position, whereas your onsite matrix elements could potentially depend >> on other things (e.g. the lattice that the site is from) >> >> >> Happy Kwanting, >> >> >> Joe >> > -- Abbout Adel
