Hi Matthew Turk, After I set ds.periodicity = (True, True, True), it can calculate the derived field without error info, thank you! However, when I tried to use SlicePlot for drawing the derived field, it raised RuntimeError that I do not know why. It seems that there is a function in YT(_fill_fields) failing to work. The version of my YT is 3.5.0. Here is the error info: ------------------------------------------------------------------------------------------------------------------------- P003 yt : [ERROR ] 2022-01-27 11:37:18,376 RuntimeError: 194 application called MPI_Abort(MPI_COMM_WORLD, 1) - process 3 195 command in line argument 196 loading data 197 File "vorfield.py", line 89, in <module> 198 slc = yt.SlicePlot(ds,"z",("boxlib","vort_z"),width=((0.08,'cm'),(0.04,'cm')),center=([0.20,0.02,0.01],'cm')) 199 File "/anaconde/envs/test/lib/python3.8/site-packages/yt/visualization/plot_window.py", line 1986, in SlicePlot 200 return AxisAlignedSlicePlot(ds, normal, fields, *args, **kwargs) 201 File "/anaconde/envs/test/lib/python3.8/site-packages/yt/visualization/plot_window.py", line 1282, in __init__ 202 slc.get_data(fields) 203 File "/anaconde/envs/test/lib/python3.8/site-packages/yt/data_objects/data_containers.py", line 1583, in get_data 204 self._generate_fields(fields_to_generate) 205 File "/anaconde/envs/test/lib/python3.8/site-packages/yt/data_objects/data_containers.py", line 1603, in _generate_fields 206 fd = self._generate_field(field) 207 File "/anaconde/envs/test/lib/python3.8/site-packages/yt/data_objects/data_containers.py", line 293, in _generate_field 208 tr = self._generate_fluid_field(field) 209 File "/anaconde/envs/test/lib/python3.8/site-packages/yt/data_objects/data_containers.py", line 311, in _generate_fluid_field 210 rv = self._generate_spatial_fluid(field, ngt_exception.ghost_zones) 211 File "/anaconde/envs/test/lib/python3.8/site-packages/yt/data_objects/data_containers.py", line 341, in _generate_spatial_fluid 212 gz[field][ngz:-ngz, ngz:-ngz, ngz:-ngz], 213 File "/anaconde/envs/test/lib/python3.8/site-packages/yt/data_objects/data_containers.py", line 256, in __getitem__ 214 self.get_data(f) 215 File "/anaconde/envs/test/lib/python3.8/site-packages/yt/data_objects/construction_data_containers.py", line 691, in get_data 216 if len(fill) > 0: self._fill_fields(fill) 218 File "/anaconde/envs/test/lib/python3.8/site-packages/yt/data_objects/construction_data_containers.py", line 1060, in _fill_fields 219 raise RuntimeError -------------------------------------------------------------------------------------------------------------------------- Thank you again for helping me! Best wishes, He Yifeng