diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 15152a09ca..bcc3b0f7c1 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1561,9 +1561,9 @@ endif()
 
 list(APPEND CP2K_SRCS_C ${CP2K_DBM_SRCS_C} ${CP2K_GRID_SRCS_C})
 
-list(APPEND CP2K_SRCS_F openPMD.F input/cp_output_handling_openpmd.F
+list(APPEND CP2K_SRCS_F openpmd_api.F input/cp_output_handling_openpmd.F
      cp_realspace_grid_openpmd.F pw/realspace_grid_openpmd.F)
-list(APPEND CP2K_SRCS_CPP openPMD.cpp)
+list(APPEND CP2K_SRCS_CPP openpmd_c_api.cpp)
 
 # ##############################################################################
 # check that the files registered in CMakeLists.txt are all present and return
diff --git a/src/input/cp_output_handling_openpmd.F b/src/input/cp_output_handling_openpmd.F
index 674e48cc2b..df5576b5b0 100644
--- a/src/input/cp_output_handling_openpmd.F
+++ b/src/input/cp_output_handling_openpmd.F
@@ -73,16 +73,16 @@ MODULE cp_output_handling_openpmd
 
 #ifdef __OPENPMD
    TYPE :: cp_openpmd_per_call_value_type
-      TYPE(openpmd_series_type) :: series
-      TYPE(openpmd_iteration_type) :: iteration
-      ! TYPE(openpmd_mesh_type) :: mesh
-      ! TYPE(openpmd_particle_species_type) :: particle_species
-      CHARACTER(len=default_string_length) :: name_prefix ! e.g. 'WFN_00008_1'
+      TYPE(openpmd_series_type) :: series = openpmd_series_type()
+      TYPE(openpmd_iteration_type) :: iteration = openpmd_iteration_type()
+      ! TYPE(openpmd_mesh_type) :: mesh = openpmd_mesh_type()
+      ! TYPE(openpmd_particle_species_type) :: particle_species = openpmd_particle_species_type()
+      CHARACTER(len=default_string_length) :: name_prefix = "" ! e.g. 'WFN_00008_1'
    END TYPE cp_openpmd_per_call_value_type
 
    TYPE :: cp_openpmd_per_call_type
-      INTEGER :: key ! unit_nr
-      TYPE(cp_openpmd_per_call_value_type) :: value
+      INTEGER :: key = -1 ! unit_nr
+      TYPE(cp_openpmd_per_call_value_type) :: value = cp_openpmd_per_call_value_type()
    END TYPE cp_openpmd_per_call_type
 
    TYPE :: cp_current_iteration_counter_type
@@ -93,16 +93,16 @@ MODULE cp_output_handling_openpmd
 
    TYPE :: cp_openpmd_per_callsite_value_type
       ! openPMD output Series.
-      TYPE(openpmd_series_type) :: output_series
+      TYPE(openpmd_series_type) :: output_series = openpmd_series_type()
       ! Information on the last Iteration that was written to, including
       ! CP2Ks complex Iteration number and its associated contiguous scalar
       ! openPMD Iteration number.
-      TYPE(cp_current_iteration_counter_type) :: iteration_counter
+      TYPE(cp_current_iteration_counter_type) :: iteration_counter = cp_current_iteration_counter_type()
    END TYPE cp_openpmd_per_callsite_value_type
 
    TYPE :: cp_openpmd_per_callsite_type
-      CHARACTER(len=default_string_length) :: key ! openpmd_basename
-      TYPE(cp_openpmd_per_callsite_value_type) :: value
+      CHARACTER(len=default_string_length) :: key = "" ! openpmd_basename
+      TYPE(cp_openpmd_per_callsite_value_type) :: value = cp_openpmd_per_callsite_value_type()
    END TYPE cp_openpmd_per_callsite_type
 
    !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
diff --git a/src/openPMD.F b/src/openpmd_api.F
similarity index 99%
rename from src/openPMD.F
rename to src/openpmd_api.F
index f8ca81001d..7ab32530c1 100644
--- a/src/openPMD.F
+++ b/src/openpmd_api.F
@@ -5,7 +5,7 @@
 !   SPDX-License-Identifier: GPL-2.0-or-later                                                      !
 !--------------------------------------------------------------------------------------------------!
 
-MODULE openPMD_api
+MODULE openpmd_api
 
 #ifdef __OPENPMD
 
@@ -1041,4 +1041,4 @@ MODULE openPMD_api
 #endif
          ! In two lines of this file, `make pretty` applies a wrong indentation and keeps it for the rest of this file.
          ! Hence, we end up a bit further to the right than we should.
-      END MODULE openPMD_api
+      END MODULE openpmd_api
diff --git a/src/openPMD.cpp b/src/openpmd_c_api.cpp
similarity index 100%
rename from src/openPMD.cpp
rename to src/openpmd_c_api.cpp
diff --git a/src/qs_scf_post_gpw.F b/src/qs_scf_post_gpw.F
index 4fb124f3cc..288e549e60 100644
--- a/src/qs_scf_post_gpw.F
+++ b/src/qs_scf_post_gpw.F
@@ -233,11 +233,11 @@ MODULE qs_scf_post_gpw
    ! or not, and on whether it has been activated in the Cube or openPMD variant.
    ! Create with function cube_or_openpmd(), see there for further details.
    TYPE cp_section_key
-      CHARACTER(len=default_string_length) :: relative_section_key ! e.g. PRINT%MO_CUBES
-      CHARACTER(len=default_string_length) :: absolute_section_key ! e.g. DFT%PRINT%MO_CUBES
-      CHARACTER(len=7) :: format_name ! 'openPMD' or 'Cube', for logging
-      INTEGER :: grid_output ! either 1 for grid_output_cubes or 2 for grid_output_openpmd
-      LOGICAL :: do_output
+      CHARACTER(len=default_string_length) :: relative_section_key = "" ! e.g. PRINT%MO_CUBES
+      CHARACTER(len=default_string_length) :: absolute_section_key = "" ! e.g. DFT%PRINT%MO_CUBES
+      CHARACTER(len=7) :: format_name = "" ! 'openPMD' or 'Cube', for logging
+      INTEGER :: grid_output = -1 ! either 1 for grid_output_cubes or 2 for grid_output_openpmd
+      LOGICAL :: do_output = .FALSE.
    CONTAINS
       ! Open a file as either Cube or openPMD
       PROCEDURE, PUBLIC :: print_key_unit_nr => cp_forward_print_key_unit_nr
diff --git a/tools/conventions/conventions.supp b/tools/conventions/conventions.supp
index f594f542c2..c62d9c641a 100644
--- a/tools/conventions/conventions.supp
+++ b/tools/conventions/conventions.supp
@@ -38,6 +38,7 @@ cp_lbfgs.F: Found WRITE statement with hardcoded unit in "subsm" https://cp2k.or
 cp_log_handling.F: Found WRITE statement with hardcoded unit in "cp_int_to_string" https://cp2k.org/conv#c012
 cp_log_handling.F: Found WRITE statement with hardcoded unit in "cp_logger_get_default_unit_nr" https://cp2k.org/conv#c012
 cp_log_handling.F: Found WRITE statement with hardcoded unit in "cp_real_dp_to_string" https://cp2k.org/conv#c012
+cp_output_handling_openpmd.F: Found type cp_openpmd_per_call_value_type without initializer https://cp2k.org/conv#c016
 cp_parser_inpp_methods.F: Found READ with unchecked STAT in "inpp_process_directive" https://cp2k.org/conv#c001
 cube_utils.F: Found WRITE statement with hardcoded unit in "return_cube_nonortho" https://cp2k.org/conv#c012
 d3_poly.F: Found CALL RANDOM_NUMBER in procedure "poly_random" https://cp2k.org/conv#c104
diff --git a/tools/precommit/precommit.py b/tools/precommit/precommit.py
index 17339c35e0..db13b6ab56 100755
--- a/tools/precommit/precommit.py
+++ b/tools/precommit/precommit.py
@@ -225,12 +225,8 @@ def process_file(fn: str, allow_modifications: bool) -> None:
         run_remote_tool("clangformat", fn)
 
     if re.match(r".*\.(cc|cpp|cxx|hcc|hpp|hxx)$", fn):
-        if (
-            fn.endswith("/torch_c_api.cpp")
-            or fn.endswith("/ace_c_api.cpp")
-            or fn.endswith("/openPMD.cpp")
-        ):
-            # Begrudgingly tolerated because PyTorch/Ace/openPMD have no C API.
+        if basename in ["torch_c_api.cpp", "ace_c_api.cpp", "openpmd_c_api.cpp"]:
+            # Begrudgingly tolerated because some libraries have no C API.
             run_remote_tool("clangformat", fn)
         else:
             raise Exception(f"C++ is not supported.")