Update theory authored by Philipp Rüssmann's avatar Philipp Rüssmann
...@@ -24,8 +24,8 @@ Thus by knowing the GF one can extract the ...@@ -24,8 +24,8 @@ Thus by knowing the GF one can extract the
systems properties, i.e. the expectation value $`\langle systems properties, i.e. the expectation value $`\langle
\mathcal{A}\rangle`$ of an operator $`\hat{\mathcal{A}}`$: \mathcal{A}\rangle`$ of an operator $`\hat{\mathcal{A}}`$:
```math ```math
\langle\mathcal{A}\rangle=-\frac{1}{\pi}\mathrm{Im}\int_{-\infty}^{E_F}\mathrm{d}E\mathrm{Tr}\left\[ \langle\mathcal{A}\rangle=-\frac{1}{\pi}\mathrm{Im}\int_{-\infty}^{E_F}\mathrm{d}E\mathrm{Tr}\left[
\hat{\mathcal{A}}\mathcal{G}(E) \right\] \hat{\mathcal{A}}\mathcal{G}(E) \right]
``` ```
For example the density For example the density
$`\rho`$ can be calculated via $`\rho`$ can be calculated via
...@@ -41,8 +41,8 @@ which gives the exression ...@@ -41,8 +41,8 @@ which gives the exression
where the second where the second
expression is the formulation in the KKR formalism where all quantities expression is the formulation in the KKR formalism where all quantities
are expressed in atom centered (at $`\vec{R}^n`$) voronoi cells and are expressed in atom centered (at $`\vec{R}^n`$) voronoi cells and
therein expanded in real spherical harmonics $`Y_L(\hat{r})`$. {{ therein expanded in real spherical harmonics $`Y_L(\hat{r})`$.
:kkrimp/voronoi_cells.png?600 \|Division of space in KKR formalism}} ![Division of space in KKR formalism](uploads/c14e758bc8d197dc5f6c369e845e72b4/voronoi_cells.png)
## Impurity embedding ## Impurity embedding
...@@ -95,9 +95,9 @@ contribution and a multiple scattering or backscattering contribution. ...@@ -95,9 +95,9 @@ contribution and a multiple scattering or backscattering contribution.
Then the charge density at the atomic site $`n`$ is given by Then the charge density at the atomic site $`n`$ is given by
```math ```math
\rho_L^{n}(r)=-\frac{1}{\pi}\int_{-\infty}^{E_F}\mathrm{d}E\left\[ \rho_L^{n}(r)=-\frac{1}{\pi}\int_{-\infty}^{E_F}\mathrm{d}E\left[
\underline{R}_L^n(r;E)\underline{\overline{S}}_L^n(r;E)+\underline{R}_L^n(r;E)\underline{\underline{G}}^{nn}\underline{\overline{G}}_L^n(r;E) \underline{R}_L^n(r;E)\underline{\overline{S}}_L^n(r;E)+\underline{R}_L^n(r;E)\underline{\underline{G}}^{nn}\underline{\overline{G}}_L^n(r;E)
\right\] \right]
``` ```
Where the expression in square brackets is the Trace over Where the expression in square brackets is the Trace over
the Green function and the first part is called single-site contribution the Green function and the first part is called single-site contribution
...@@ -115,8 +115,8 @@ positions vanish, i.e. $`\Delta t=0`$. This allows us to embed the ...@@ -115,8 +115,8 @@ positions vanish, i.e. $`\Delta t=0`$. This allows us to embed the
impurity in a finite real space cluster into the host system. The impurity in a finite real space cluster into the host system. The
calculation is then done as follows. calculation is then done as follows.
* Compute the host systems Green function and write out the structural Green function as well as the single-site $`t`$ matrix of the host $`t_{\mathrm{host}}`$. - Compute the host systems Green function and write out the structural Green function as well as the single-site $`t`$ matrix of the host $`t_{\mathrm{host}}`$.
* From the impurity potential compute the $`t`$-matrix of the impurity and construct $`\Delta t=t_{\mathrm{host}}-t_{\mathrm{imp}}`$ - From the impurity potential compute the $`t`$-matrix of the impurity and construct $`\Delta t=t_{\mathrm{host}}-t_{\mathrm{imp}}`$
* Solve the impurity Dyson equation: $`\underline{\underline{G}}=\underline{\underline{G}}_{\mathrm{host}}+\underline{\underline{G}}_{\mathrm{host}}\Delta t\underline{\underline{G}}`$ - Solve the impurity Dyson equation: $`\underline{\underline{G}}=\underline{\underline{G}}_{\mathrm{host}}+\underline{\underline{G}}_{\mathrm{host}}\Delta t\underline{\underline{G}}`$
* Compute the new impurity potential from the Green function and update the input potential - Compute the new impurity potential from the Green function and update the input potential
* Repeat steps 2.-4. until the impurity potential converges - Repeat steps 2.-4. until the impurity potential converges