Add Space class

The Space class handles the simulation space

src/md/Potentials.hpp

@@ -11,8 +11,21 @@
 
 #pragma once
 
+#include <cmath>
+
 class Potential {
 public:
   virtual double potential(double r) = 0;
   virtual double force(double r)     = 0;
+};
+
+class LennardJones : public Potential {
+public:
+  double potential(double r) override {
+    return 4 * (std::pow(r, -12) - std::pow(r, -6));
+  }
+
+  double force(double r) override {
+    return 24 * (2 * std::pow(r, -13) - std::pow(r, -7));
+  }
 };