Dear Mengqiu: Transiesta is designed to give accurate calculations of larger currents, it is designed for the contact regime (as opposed to the tunneling regime).
So it is not supposed to be accurate in the tunneling regime because the description of the tunneling barrier itself is not accurate, and the numerical error is close to the values obtained for that case. You will certainly obtain some values for that tunneling configuration, but use them at your own risk! My suggestion is to change the configuration to try to make the tunneling regime as "little tunneling" as possible (currents of about 100 nA per atom or larger) and try to conclude the physics of the system from there. Yours Jose A. On Thu, 2010-06-17 at 15:08 +0000, CaiMeng-Qiu wrote: > Dear Jose A. Torres > > > In the examples you show probably the Kx,Ky mesh is > > not converged yet. (But it seems to me in any case > > that you are getting different expressions for a numerical > > "zero" for the current.) > > My system is tunneling junction with insulated barrier. Can the > Transiesta calculation distinguish the tiny current? > > Thank you again! > > Sincerely, > > Mengqiu > > >> > > > > On Thu, 2010-06-17 at 13:04 +0000, CaiMeng-Qiu wrote: > > > Dear Jose A. Torres： > > > > > > Thank you very much again! > > > I also several questions for these. > > > > > > > > > > > > > > > > > > On Thu, 2010-06-17 at 11:54 +0000, CaiMeng-Qiu wrote: > > > > > Dear Jose A. Torres： > > > > > > > > > > Thank you much for your explanation in detail. > > > > > > > > > > > > > > > > > - Also choose a large enough number of points to > > > > > > describe the function T(E) properly! (it may > > > > > > have sharp peaks) > > > > > > > > > > Do you mean I should adopt the dense k-mesh and large value of > > > > > TSTBT.NPoints? > > > > > > > > Here I just mean a TSTBT.NPoints to be large enough.> > > > > > > > In the TRANSIESTA-manual, it mentions:" In the case of tbtrans, > the > > > k-point sampling has to be specified also using a > kgrid_Monkhorst_Pack > > > block, and can differ from the sampling that was used in the > > > TRANSIESTA calculation. The convergence of the transmission > function > > > with respect to the k sampling can be slower than the one for the > > > density matrix. This means that one may have to increase the > number of > > > k-points used in tbtrans." Did it mean that we adopt the dense > k-mesh > > > for the tbtrans calcualtion after the Transiesta calculation? > > > > > > I do find that, for the special TSTBT.NPoints, the varied k-mesh > in > > > the xy-plane generate the changed current. > > > For examplefor the tbtrans calcultions: > > > v -1.0 eV > > > TSTBT.NPoints 1500 > > > k-mesh 6x6x50 > > > I=-3.17E-16 > > > > > > where: > > > v -1.0 eV > > > TSTBT.NPoints 1500 > > > k-mesh 6x6x70 > > > I=-3.17E-16 > > > > > > where: > > > > > > v -1.0 eV > > > TSTBT.NPoints 1500 > > > k-mesh 7x7x60 > > > I=-2.94E-16 > > > > > > where: > > > v -1.0 eV > > > TSTBT.NPoints 1500 > > > k-mesh 8x8x60 > > > I=-3.59E-16 > > > > > > If i should check both the k-mesh and TSTBT.NPoints for the > > > calculated current? > > > > > > Thank you in advance! > > > > > > Sincerely, > > > > > > Mengqiu > > > > > > > > > > > > > > > > > Generally, how much is it for the value of TS.TBT.NPoints? > > > > > > > > A few hundreds to a few thousand points. > > > > > > > > > > > > > > Thank you very much again! > > > > > > > > > > Sincerely, > > > > > > > > > > Mengqiu > > > > > > > > > > > > > > > > > > > > > ______________________________________________________________________ > > > 使用新一代 Windows Live Messenger 轻松交流和共享！ 立刻下载！ > > > > > > > > ______________________________________________________________________ > 搜索本应是彩色的,快来体验新一代搜索引擎-必应,精美图片每天换哦! 立即试 > 用！
