message: Bugfix: geometrically illegal interaction pairs are now discarded.
  When an interaction pair goes beyond the geometry of the sample it is ignored in `Vectormath::idx_from_pair`.
diff: @@ -131,6 +131,12 @@ namespace Engine
  auto& Nb = n_cells[1];
  auto& Nc = n_cells[2];
  + // Invalid index if translations reach out over the lattice bounds
  + if (std::abs(pair.translations[0]) > Na ||
  + std::abs(pair.translations[1]) > Nb ||
  + std::abs(pair.translations[2]) > Nc )
  + return -1;
  +
  // Translations (cell) of spin i
  int nic = ispin / (N*Na*Nb);
  int nib = (ispin - nic*N*Na*Nb) / (N*Na);
  @@ -248,6 +254,12 @@ namespace Engine
  auto& Nb = n_cells[1];
  auto& Nc = n_cells[2];
  + // Invalid index if translations reach out over the lattice bounds
  + if (std::abs(pair.translations[0]) > Na ||
  + std::abs(pair.translations[1]) > Nb ||
  + std::abs(pair.translations[2]) > Nc )
  + return -1;
  +
  // Translations (cell) of spin i
  int nic = ispin / (N*Na*Nb);
  int nib = (ispin - nic*N*Na*Nb) / (N*Na);
  