Structure

[HIMANI]

I have made a hydrogen passivated Si-SiO2-amor Al2O3 inerface. I am trying to optimise the structure for further calculation but it is taking very much time. I have attached my structure file. Please check and tell me whether my structure is correct or not.

[Umberto Martinez]

You should definitely have a second look at your structure.
We cannot really say if the structure is correct or not, since it is really up to you and we do not know what you want to simulate.
However, passivation looks done in the wrong way.
Also it is not clear if you want to simulate a surface/slab or a bulk system.

Finally, the optimization is probably taking long time because your structure is very far from equilibrium.
But you should attach the whole input file if you want more hints.

Last suggestion, in the geometry optimization analysis specify the trajectory file. In this case you will be able to monitor the optimization process.

[HIMANI]

Hello Sir,
My structure is basically a solar cell structure where we are depositing Al2O3 on Silicon wafer. I have kept a SiO2 layer between Al2O3 and Si as experimentally it is well known that some amount of SiO2 is always present on the Si wafer. So, it is a Si wafer(330 Micrometer around) having SiO2 over it( 1 to 2 nm) and then a thin film of Al2O3(2 to 3 nm). Also, when the wafer is annealed hydrogen from the bulk of Al2O3 releases and passivates the dangling bonds at the interface. That is why hydrogen passivation is applied. Now, please tell me where i am wrong according to the specification of my structure.

[Umberto Martinez]

1- Your structure is yes a Si|SiO2|Al2O3 interface but it is periodic in the C direction making it a  Si|SiO2|Al2O3|Si|SiO2|Al2O3|Si|SiO2|Al2O3|....... system.
Try to repeat your structure along the C direction.
From what you say you should add a vacuum region below the Si side and above the Al2O3 side.
In this way you will have a simple Si|SiO2|Al2O3 interface.

2- I cannot tell you if the passivation is correct or wrong. this is up to your and your research.
My comment about the passivation being wrong is merely an observation.