From 6d3bf1ea8907de654dade1dbb91e88e3657261d6 Mon Sep 17 00:00:00 2001
From: Jan Drewniok <97012901+Drewniok@users.noreply.github.com>
Date: Wed, 19 Apr 2023 11:14:49 +0200
Subject: [PATCH] :art: Changed the unit of the lambda-tf physical parameter
 from meter to nanometer (#188)

* :art: Unit of `lambda_tf` is changed from meter to nanometer.

* :art: `epsilon_r` is unit-less.
---
 .../sidb/sidb_simulation_parameters.hpp       | 20 +++++++++----------
 .../charge_distribution_surface.hpp           |  2 +-
 .../charge_distribution_surface.cpp           |  2 +-
 3 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/include/fiction/algorithms/simulation/sidb/sidb_simulation_parameters.hpp b/include/fiction/algorithms/simulation/sidb/sidb_simulation_parameters.hpp
index da8db5c17..c684c363f 100644
--- a/include/fiction/algorithms/simulation/sidb/sidb_simulation_parameters.hpp
+++ b/include/fiction/algorithms/simulation/sidb/sidb_simulation_parameters.hpp
@@ -27,14 +27,14 @@ struct sidb_simulation_parameters
      * @param mu_minus it is the energy transition level (0/-).
      * @param relative_permittivity it describes the electric field reduction due to polarization.
      * @param screening_distance also known as "Thomas-Fermi screening" and it describes the electric field screening
-     * due to free charges.
+     * due to free charges in nm.
      * @param a lattice constant in Å (Ångström).
      * @param b lattice constant in Å.
      * @param c lattice constant in Å.
      */
     constexpr explicit sidb_simulation_parameters(const uint8_t base_number = 3, const double mu_minus = -0.32,
                                                   const double relative_permittivity = 5.6,
-                                                  const double screening_distance = 5.0 * 1E-9, const double a = 3.84,
+                                                  const double screening_distance = 5.0, const double a = 3.84,
                                                   const double b = 7.68, const double c = 2.25) :
             lat_a{a},
             lat_b{b},
@@ -51,35 +51,35 @@ struct sidb_simulation_parameters
     }
 
     /**
-     * lat_a is the lattice vector in x-direction.
+     * lat_a is the lattice vector in x-direction (unit: Å).
      */
     double lat_a;
     /**
-     * lat_b is the lattice vector in y-direction.
+     * lat_b is the lattice vector in y-direction (unit: Å).
      */
     double lat_b;
     /**
-     * lat_c is the dimer pair separation.
+     * lat_c is the dimer pair separation (unit: Å).
      */
     double lat_c;
     /**
-     * epsilon_r is the electric permittivity. It is a material specific number.
+     * epsilon_r is the electric permittivity. It is a material specific number (unit-less).
      */
     double epsilon_r;
     /**
-     * k is the Coulomb constant and is inversely proportional to the electric permittivity.
+     * k is the Coulomb constant and is inversely proportional to the electric permittivity (unit: SI).
      */
     double k;
     /**
-     * lambda_tf is the Thomas-Fermi screening distance.
+     * lambda_tf is the Thomas-Fermi screening distance (unit: nm).
      */
     double lambda_tf;
     /**
-     * µ- is the energy transition level (0/-)
+     * µ- is the energy transition level (0/-) (unit: eV).
      */
     double mu;
     /**
-     * µ+ is the energy transition level (+/0)
+     * µ+ is the energy transition level (+/0) (unit: eV).
      */
     double mu_p;
     /**
diff --git a/include/fiction/technology/charge_distribution_surface.hpp b/include/fiction/technology/charge_distribution_surface.hpp
index 1be588511..6ed91c72e 100644
--- a/include/fiction/technology/charge_distribution_surface.hpp
+++ b/include/fiction/technology/charge_distribution_surface.hpp
@@ -481,7 +481,7 @@ class charge_distribution_surface<Lyt, false> : public Lyt
         }
 
         return (strg->phys_params.k / (strg->nm_dist_mat[index1][index2] * 1E-9) *
-                std::exp(-strg->nm_dist_mat[index1][index2] * 1E-9 / strg->phys_params.lambda_tf) *
+                std::exp(-strg->nm_dist_mat[index1][index2] / strg->phys_params.lambda_tf) *
                 physical_constants::ELECTRIC_CHARGE);
     }
     /**
diff --git a/test/technology/charge_distribution_surface.cpp b/test/technology/charge_distribution_surface.cpp
index a344baabb..8ebdade55 100644
--- a/test/technology/charge_distribution_surface.cpp
+++ b/test/technology/charge_distribution_surface.cpp
@@ -417,7 +417,7 @@ TEMPLATE_TEST_CASE(
     SECTION("using chargeless and normal potential function")
     {
         TestType                         lyt_new{{11, 11}};
-        const sidb_simulation_parameters params{3, -0.32, 5.0 * 1E-9, 3.84 * 1E-10, 7.68 * 1E-10, 2.25 * 1E-10};
+        const sidb_simulation_parameters params{3, -0.32, 5.0, 3.84, 7.68, 2.25};
 
         lyt_new.assign_cell_type({0, 0, 1}, TestType::cell_type::NORMAL);
         lyt_new.assign_cell_type({1, 3, 0}, TestType::cell_type::NORMAL);