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