exercises:2016_uzh_cmest:defects_in_graphene
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| exercises:2016_uzh_cmest:defects_in_graphene [2016/11/14 08:28] – [Displacements] tmueller | exercises:2016_uzh_cmest:defects_in_graphene [2020/08/21 10:15] (current) – external edit 127.0.0.1 | ||
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| Quick question: Does it matter which carbon atom you remove? (hint: what kind of boundary conditions do we impose?) | Quick question: Does it matter which carbon atom you remove? (hint: what kind of boundary conditions do we impose?) | ||
| - | Calculate the energy of the vacancy formation, that is $E_v = E_2 (N-1)/N \cdot E_1$ where $E_1$ is the energy of the complete system, $E_2$ that of the system with a vacancy and $N$ the number of atoms. | + | Calculate the energy of the vacancy formation, that is $E_v = E_2 - \frac{N-1}{N} \cdot E_1$ where $E_1$ is the energy of the complete system, $E_2$ that of the system with a vacancy and $N$ the number of atoms. |
| ===== Analyze the PDOS ===== | ===== Analyze the PDOS ===== | ||
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| Now we are going to investigate the effect an adsorbent has on graphene. | Now we are going to investigate the effect an adsorbent has on graphene. | ||
| - | ====== Change in energy | + | ===== Change in energy ===== |
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| Try to explain based on the lecture what might be the problem.</ | Try to explain based on the lecture what might be the problem.</ | ||
| - | ====== Displacements | + | ===== Displacements ===== |
| We are furthermore interested in the change of structure this adsorbent causes. Try to visualize which atoms have to assume a new position in order to minimize the total energy. That is: plot $\sqrt{(x^i-x^i_0)^2 + (y^i-y^i_0)^2 + (z^i-z^i_0)^2}$ in a sensible manner (one which also retains the geometry of graphene). | We are furthermore interested in the change of structure this adsorbent causes. Try to visualize which atoms have to assume a new position in order to minimize the total energy. That is: plot $\sqrt{(x^i-x^i_0)^2 + (y^i-y^i_0)^2 + (z^i-z^i_0)^2}$ in a sensible manner (one which also retains the geometry of graphene). | ||
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| + | ======= Analyzing defects in hexagonal Boron-Nitride ======= | ||
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| + | Repeat the calculations of the vacancy formation, defect formation and adsorption for the h-BN-layer structure, taking into account that now both the N and the B can be replaced. | ||
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| + | Compare the energies for the two cases, where is a vacancy more likely to be and on top of which atom does an oxygen atom preferably adsorb. | ||
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| + | <note tip>Use the total energy of a B or N atom when calculating the vacancy formation energy.</ | ||
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| + | Since N and B are radicals, you have to include the following keywords/ | ||
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| + | * '' | ||
| + | * '' | ||
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