fix for 2D PEC

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `SimulationData.mnt_data_from_file()` method to load only a single monitor data object from a simulation data `.hdf5` file.
 - `_hash_self` to base model, uses `hashlib` to hash a Tidy3D component the same way every session.
 - `ComponentModeler.plot_sim_eps()` method to plot the simulation permittivity and ports.
+- Support for 2D PEC materials.
 
 ### Changed
 - Indent for the json string of Tidy3D models has been changed to `None` when used internally; kept as `indent=4` for writing to `json` and `yaml` files.
@@ -30,6 +31,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Restrict to `matplotlib` >= 3.5, avoiding bug in plotting `CustomMedium`.
 - Fixes `ComponentModeler` batch file being different in different sessions by use of deterministic hash function for computing batch filename.
 - Can pass `kwargs` to `ComponentModeler.plot_sim()` to use in `Simulation.plot()`.
+- Fixed a couple bugs in the handling of 2D PEC materials.
+
 
 ## [2.5.0rc2] - 2023-10-30
 

tidy3d/components/simulation.py

@@ -2703,7 +2703,11 @@ def get_neighboring_media(
             # get neighboring media and grid sizes
             (neighbors, dls) = get_neighboring_media(geometry, axis, background_structures)
 
-            new_bounds = (center - dls[0] / 2, center + dls[1] / 2)
+            if not structure.medium.is_pec:
+                new_bounds = (center - dls[0] / 2, center + dls[1] / 2)
+            else:
+                new_bounds = (center, center)
+
             new_geometry = set_bounds(structure.geometry, bounds=new_bounds, axis=axis)
 
             new_medium = structure.medium.volumetric_equivalent(