Band structure of cobalt adsorbed graphene

In summary, the speaker completed computations of the band structure of cobalt adsorbed graphene using DFT implemented with quantum espresso. They found that in a 3x3 supercell with one cobalt atom, there was a gap between the conduction and valence band. However, in a 4x4 supercell with one cobalt atom, there was no gap. The speaker suggests that this could be due to boundary conditions or finite size effects, and recommends using finite size scaling to determine the trend. They also note that the two systems have different densities of cobalt atoms, which could affect the interaction between them and the correct interpretation depends on the desired physical system. Minor factors such as the positioning of the cobalt atoms over
  • #1
saroj
2
0
I have done the computations of band structure of cobalt adsorbed graphene. In 3x3 supercell of cobalt adsorbed (one cobalt atom) graphne, there is opening of band that is gap between conduction and valence band but there is no gap in 4x4 supercell of cobalt adsorbed graphene. I've done this in DFT implemented with quantum espresso. what is reason for the difference?
 
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  • #2
Well, I'm not sure how sensitive DFT is to these things or how the specific material is supposed to behave, but in other simulations one often needs to pay attention to boundary conditions (you can check if you have an even-odd effect when changing cell size) and to finite size effects. For the latter, the finite size of the system may open up a gap which disappears at some point when taking the thermodynamic limit. The only way around this is to measure the gap for a number of system sizes and see if there's a trend or not (you may want more than two data points though), a practice called finite size scaling. Could it be either of these things?
 
  • #3
These are also different physical systems, due to the implied periodicity of these calculations. The first has a density of one Co atom per 3x3 cell of graphene, versus one Co atom per 4x4 cell of graphene - so the second implies a lower density of Co ad-atoms, and therefore a reduced Co-Co interaction. Thus the answer to "which is correct" depends on the physical system you are interested in, i.e. what physical Co density. Other minor things like how you position the Co over the C atoms of graphene can also make a difference ...
 

1. What is the band structure of cobalt adsorbed graphene?

The band structure of cobalt adsorbed graphene refers to the energy levels of electrons in the material. It shows how electrons are allowed to move through the material and how they interact with each other. The band structure can be affected by the presence of cobalt atoms, which can change the electronic properties of graphene.

2. How does cobalt adsorption affect the band structure of graphene?

Cobalt adsorption can introduce new energy levels in the band structure of graphene, leading to changes in its electronic properties such as conductivity and magnetism. This is because the cobalt atoms can interact with the electrons in graphene, altering their energy levels and behavior.

3. What techniques are used to study the band structure of cobalt adsorbed graphene?

Some common techniques used to study the band structure of cobalt adsorbed graphene include angle-resolved photoemission spectroscopy (ARPES), scanning tunneling microscopy (STM), and X-ray photoelectron spectroscopy (XPS). These techniques can provide information about the electronic structure and properties of the material at the atomic scale.

4. How does the band structure of cobalt adsorbed graphene impact its potential applications?

The band structure of cobalt adsorbed graphene can greatly impact its potential applications. For example, the presence of cobalt atoms can introduce magnetic properties in graphene, making it useful for spintronics and magnetic storage devices. Additionally, changes in the band structure can also affect the material's electrical conductivity, making it useful for electronic and optoelectronic devices.

5. Are there any challenges in studying the band structure of cobalt adsorbed graphene?

Yes, there are several challenges in studying the band structure of cobalt adsorbed graphene. One challenge is the difficulty in controlling the amount and distribution of cobalt atoms on the graphene surface. Another challenge is the strong interaction between cobalt and graphene, which can make it challenging to distinguish the electronic contributions of each component. Additionally, the highly localized nature of the cobalt atoms can make it difficult to obtain a comprehensive understanding of the material's electronic properties.

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