Minor changes

README.md

@@ -57,7 +57,7 @@ With this, the Coulomb matrix elements between four plane-waves can be written a
 ```math
 \begin{gather*}
 \bra{pq}V_C\ket{rs}=\int e^{-i(q-r)\cdot r_2}  e^{-i(p-s)\cdot r_2} \frac{4\pi}{|p-s|^2} \mathrm{d}r_2=\\
-\frac{4\pi}{|p-s|^2}\int e^{-i\left[(p-s)-(r-q)\right]\cot r_2} \mathrm{d}r_2=\\
+\frac{4\pi}{|p-s|^2}\int e^{-i\left[(p-s)-(r-q)\right]\cdot r_2} \mathrm{d}r_2=\\
 \frac{4\pi}{|p-s|^2}\delta\left((p-s)-(r-q)\right)\,,
 \end{gather*}
 ```
@@ -92,6 +92,7 @@ $$h_{tuvw}=\sum_{\substack{p, p \neq 0}} \frac{4\pi}{|p|^2} \rho^\ast_{tw}(p) \r
 
 **Notes:**
 - We perform a spin-less DFT calculation. Therefore, the Kohn-Sham orbitals we use from the DFT calculation do not include spin. For the VQE and FCI calculation we use each Kohn-Sham orbital as a spin orbital which can hold two electrons, one with spin-up one with spin-down. Therefore 2 occupied Kohn-Sham orbitals correspond to 4 electrons, each occupying one spin orbital.
+- The calculation of ERIs via pair densities is currently only implemented for $\Gamma$-point calculations.
 - The implementation of calculation the ERIs via pair densities is inspired by [WEST](https://west-code.org/) and its implementation on [GitHub](https://github.com/west-code-development/West), especially the code in the [compute_eri_vc function](https://github.com/west-code-development/West/blob/master/Wfreq/solve_eri.f90#L327). Publications related when citing WEST: [Large Scale GW Calculations, M. Govoni and G. Galli, J. Chem. Theory Comput. 11, 2680 (2015)](https://pubs.acs.org/doi/10.1021/ct500958p) and [GPU Acceleration of Large-Scale Full-Frequency GW Calculations, V. Yu and M. Govoni, J. Chem. Theory Comput. 18, 4690 (2022)](https://pubs.acs.org/doi/10.1021/acs.jctc.2c00241). We note that, although inspiration was taken from the WEST implementation, no code from WEST was used.
 
 

eri_pair_densities.py

@@ -1,9 +1,4 @@
-import os
 import numpy as np
-from scipy import signal
-import xmltodict
-from wfc import Wfc
-import calc_matrix_elements
 
 # Calculate ERIs via h_ijkl = 4\pi \sum_p (\rho*_il(p) \rho_jk(p))/p²
 # with \rho_ij(p)=\int dr \rho_ij(r) e^(-ipr) which is the Fourier transform of

main.py

@@ -39,21 +39,24 @@
         p, c_ip_orbitals, wfc1_ncpp.atoms, wfc1_ncpp.cell_volume
     )
 
-    # Electron repulsion
-    eri_file = os.path.join("eri", "eri_sym_rs_tuvw_0_4_f64.txt")
-
-    (
-        n_elements_pqrs,
-        n_states_pqrs,
-        indices_pqrs,
-        mat_pqrs,
-    ) = load_eri_from_file(eri_file, "tuvw")
-    eri_hashmap = EriHashmap()
-    eri_hashmap.update(indices_pqrs, mat_pqrs)
-    h_pqrs: np.ndarray = eri_hashmap.get_tuvw(orbitals_indices) / wfc1_ncpp.cell_volume
+    # # Load Electron repulsion integrals from Rust calculation
+    # eri_file = os.path.join("eri", "eri_sym_rs_tuvw_0_4_f64.txt")
+
+    # (
+    #     n_elements_pqrs,
+    #     n_states_pqrs,
+    #     indices_pqrs,
+    #     mat_pqrs,
+    # ) = load_eri_from_file(eri_file, "tuvw")
+    # eri_hashmap = EriHashmap()
+    # eri_hashmap.update(indices_pqrs, mat_pqrs)
+    # h_pqrs: np.ndarray = eri_hashmap.get_tuvw(orbitals_indices) / wfc1_ncpp.cell_volume
 
     # Cacluate ERIs via pair density instead of loading from Rust and CUDA output
-    h_pqrs_pair_density: np.ndarray = (
+    assert (
+        wfc1_ncpp.gamma_only is True
+    ), "Calculating ERIs via pair densities is only implemented for the gamma-point!"
+    h_pqrs: np.ndarray = (
         eri_pair_densities.eri_gamma(p=p, c_ip=c_ip_orbitals) / wfc1_ncpp.cell_volume
     )