Dear experts,
I am now studying the geometry optimization of an interface based device. From the tutorial "Advanced device relaxation", we can see that the geometry optimization of such a device includes these steps:
(1) constructing the interface using the "Interface" plug-in;
(2) using the "device from bulk" plug-in to build the two-probe device;
(3) splitting the device into three parts: the left electrode, the right electrode and the central region;
(4) geometry optimizing the two electrodes (sometimes only one electrode needs to be optimized);
(5) applying the effect of the geometry optimization of the electrode onto the corresponding atoms in the central region by stretching the atoms;
(6) geometry optimizing the central region using Bulk Rigid Relaxation (BRR) method as described in the tutorial. Sometimes a 1DMIN method will also be used to improve the accuracy;
(7) the final device configuration can be obtained by applying "device from bulk" again onto the relaxed central region;
However, in tutorial "Modeling metal–semiconductor contacts: The Ag–Si interface", after relaxing the central region of the Ag-Si interface device, an additional "Device relaxation" was carried out. I don't know what's this step for. Is it necessary to do so?
And, it was said in this tutorial that the time consuming for the relaxation of the central region needs about 20 hours on a 16-core node, while the time consuming for the relaxation of the whole device only takes about 2 hours on 16 cores. Since the whole device is larger than the central region, why is the time consuming for the relaxation of the whole device far less than that needed for the relaxation of the central?
Thank you very much for you time and kind help!
