diff --git a/python/damask/_configmaterial.py b/python/damask/_configmaterial.py
index ed45f2662..cdeab3a53 100644
--- a/python/damask/_configmaterial.py
+++ b/python/damask/_configmaterial.py
@@ -24,6 +24,20 @@ class ConfigMaterial(Config):
         super().save(fname,**kwargs)
 
 
+    @classmethod
+    def load(cls,fname='material.yaml'):
+        """
+        Load from yaml file.
+
+        Parameters
+        ----------
+        fname : file, str, or pathlib.Path, optional
+            Filename or file for writing. Defaults to 'material.yaml'.
+
+        """
+        return super(ConfigMaterial,cls).load(fname)
+
+
     @staticmethod
     def from_table(table,constituents={},**kwargs):
         """
diff --git a/python/damask/_result.py b/python/damask/_result.py
index 3f4ca735c..f0406ecad 100644
--- a/python/damask/_result.py
+++ b/python/damask/_result.py
@@ -21,6 +21,7 @@ from . import grid_filters
 from . import mechanics
 from . import util
 
+h5py3 = h5py.__version__[0] == '3'
 
 class Result:
     """
@@ -93,7 +94,7 @@ class Result:
 
 
     def __repr__(self):
-        """Show selected data."""
+        """Show summary of file content."""
         all_selected_increments = self.selection['increments']
 
         self.pick('increments',all_selected_increments[0:1])
@@ -280,7 +281,8 @@ class Result:
                 for path_old in self.get_dataset_location(name_old):
                     path_new = os.path.join(os.path.dirname(path_old),name_new)
                     f[path_new] = f[path_old]
-                    f[path_new].attrs['Renamed'] = 'Original name: {}'.encode()
+                    f[path_new].attrs['Renamed'] = f'Original name: {name_old}' if h5py3 else \
+                                                   f'Original name: {name_old}'.encode()
                     del f[path_old]
         else:
             raise PermissionError('Rename operation not permitted')
@@ -422,8 +424,13 @@ class Result:
                             for d in f[group].keys():
                                 try:
                                     dataset = f['/'.join([group,d])]
-                                    unit  = f" / {dataset.attrs['Unit'].decode()}" if 'Unit' in dataset.attrs else ''
-                                    description = dataset.attrs['Description'].decode()
+                                    if 'Unit' in dataset.attrs:
+                                        unit = f" / {dataset.attrs['Unit']}" if h5py3 else \
+                                               f" / {dataset.attrs['Unit'].decode()}"
+                                    else:
+                                        unit = ''
+                                    description = dataset.attrs['Description'] if h5py3 else \
+                                                  dataset.attrs['Description'].decode()
                                     message += f'        {d}{unit}: {description}\n'
                                 except KeyError:
                                     pass
@@ -463,7 +470,8 @@ class Result:
     def get_crystal_structure(self):                                                                # ToDo: extension to multi constituents/phase
         """Info about the crystal structure."""
         with h5py.File(self.fname,'r') as f:
-            return f[self.get_dataset_location('orientation')[0]].attrs['Lattice'].astype('str')    # np.bytes_ to string
+            return f[self.get_dataset_location('O')[0]].attrs['Lattice'] if h5py3 else \
+                   f[self.get_dataset_location('O')[0]].attrs['Lattice'].decode()
 
 
     def enable_user_function(self,func):
@@ -788,20 +796,26 @@ class Result:
 
 
     @staticmethod
-    def _add_Mises(T_sym):
-        t = 'strain' if T_sym['meta']['Unit'] == '1' else \
-            'stress'
+    def _add_Mises(T_sym,kind):
+        k = kind
+        if k is None:
+            if T_sym['meta']['Unit'] == '1':
+                k = 'strain'
+            elif T_sym['meta']['Unit'] == 'Pa':
+                k = 'stress'
+        if k not in ['stress', 'strain']:
+            raise ValueError('invalid von Mises kind {kind}')
 
         return {
-                'data':  (mechanics.Mises_strain if t=='strain' else mechanics.Mises_stress)(T_sym['data']),
+                'data':  (mechanics.Mises_strain if k=='strain' else mechanics.Mises_stress)(T_sym['data']),
                 'label': f"{T_sym['label']}_vM",
                 'meta':  {
                           'Unit':        T_sym['meta']['Unit'],
-                          'Description': f"Mises equivalent {t} of {T_sym['label']} ({T_sym['meta']['Description']})",
+                          'Description': f"Mises equivalent {k} of {T_sym['label']} ({T_sym['meta']['Description']})",
                           'Creator':     'add_Mises'
                           }
                 }
-    def add_Mises(self,T_sym):
+    def add_Mises(self,T_sym,kind=None):
         """
         Add the equivalent Mises stress or strain of a symmetric tensor.
 
@@ -809,9 +823,12 @@ class Result:
         ----------
         T_sym : str
             Label of symmetric tensorial stress or strain dataset.
+        kind : {'stress', 'strain', None}, optional
+            Kind of the von Mises equivalent. Defaults to None, in which case
+            it is selected based on the unit of the dataset ('1' -> strain, 'Pa' -> stress').
 
         """
-        self._add_generic_pointwise(self._add_Mises,{'T_sym':T_sym})
+        self._add_generic_pointwise(self._add_Mises,{'T_sym':T_sym},{'kind':kind})
 
 
     @staticmethod
@@ -1035,7 +1052,7 @@ class Result:
                     loc  = f[group+'/'+label]
                     datasets_in[arg]={'data' :loc[()],
                                       'label':label,
-                                      'meta': {k:v.decode() for k,v in loc.attrs.items()}}
+                                      'meta': {k:(v if h5py3 else v.decode()) for k,v in loc.attrs.items()}}
             lock.release()
             r = func(**datasets_in,**args)
             return [group,r]
@@ -1080,17 +1097,21 @@ class Result:
                     if self._allow_modification and result[0]+'/'+result[1]['label'] in f:
                         dataset = f[result[0]+'/'+result[1]['label']]
                         dataset[...] = result[1]['data']
-                        dataset.attrs['Overwritten'] = 'Yes'.encode()
+                        dataset.attrs['Overwritten'] = 'Yes' if h5py3 else \
+                                                       'Yes'.encode()
                     else:
                         dataset = f[result[0]].create_dataset(result[1]['label'],data=result[1]['data'])
 
                     now = datetime.datetime.now().astimezone()
-                    dataset.attrs['Created'] = now.strftime('%Y-%m-%d %H:%M:%S%z').encode()
+                    dataset.attrs['Created'] = now.strftime('%Y-%m-%d %H:%M:%S%z') if h5py3 else \
+                                               now.strftime('%Y-%m-%d %H:%M:%S%z').encode()
 
                     for l,v in result[1]['meta'].items():
-                        dataset.attrs[l]=v.encode()
-                    creator = f"damask.Result.{dataset.attrs['Creator'].decode()} v{damask.version}"
-                    dataset.attrs['Creator'] = creator.encode()
+                        dataset.attrs[l]=v if h5py3 else v.encode()
+                    creator = dataset.attrs['Creator'] if h5py3 else \
+                              dataset.attrs['Creator'].decode()
+                    dataset.attrs['Creator'] = f"damask.Result.{creator} v{damask.version}" if h5py3 else \
+                                               f"damask.Result.{creator} v{damask.version}".encode()
 
                 except (OSError,RuntimeError) as err:
                     print(f'Could not add dataset: {err}.')
diff --git a/python/damask/_vtk.py b/python/damask/_vtk.py
index 10f3b482b..942be4f1f 100644
--- a/python/damask/_vtk.py
+++ b/python/damask/_vtk.py
@@ -197,11 +197,10 @@ class VTK:
         elif isinstance(self.vtk_data,vtk.vtkPolyData):
             writer = vtk.vtkXMLPolyDataWriter()
 
-        default_ext = writer.GetDefaultFileExtension()
+        default_ext = '.'+writer.GetDefaultFileExtension()
         ext = Path(fname).suffix
-        if ext and ext != '.'+default_ext:
-            raise ValueError(f'Given extension "{ext}" does not match default ".{default_ext}"')
-        writer.SetFileName(str(Path(fname).with_suffix('.'+default_ext)))
+        writer.SetFileName(str(fname)+(default_ext if default_ext != ext else ''))
+
         if compress:
             writer.SetCompressorTypeToZLib()
         else:
diff --git a/python/tests/reference/Result/12grains6x7x8_tensionY.hdf5 b/python/tests/reference/Result/12grains6x7x8_tensionY.hdf5
index 39c17fadb..6d9334d1e 100644
Binary files a/python/tests/reference/Result/12grains6x7x8_tensionY.hdf5 and b/python/tests/reference/Result/12grains6x7x8_tensionY.hdf5 differ
diff --git a/python/tests/reference/Result/6grains6x7x8_single_phase_tensionY.hdf5 b/python/tests/reference/Result/6grains6x7x8_single_phase_tensionY.hdf5
index 7812f82e8..799005217 100644
Binary files a/python/tests/reference/Result/6grains6x7x8_single_phase_tensionY.hdf5 and b/python/tests/reference/Result/6grains6x7x8_single_phase_tensionY.hdf5 differ
diff --git a/python/tests/reference/Result/material.config b/python/tests/reference/Result/material.config
deleted file mode 100644
index 4820b1eed..000000000
--- a/python/tests/reference/Result/material.config
+++ /dev/null
@@ -1,126 +0,0 @@
-<homogenization>
-[none]
-mech none
-ngrains 1
-
-<texture>
-[Grain1]
-(gauss)	phi1 358.98	Phi 65.62	phi2 24.48
-[Grain2]
-(gauss)	phi1 121.05	Phi 176.11	phi2 295.73
-[Grain3]
-(gauss)	phi1 43.79	Phi 113.76	phi2 345.90
-[Grain4]
-(gauss)	phi1 265.15	Phi 62.52	phi2 299.71
-[Grain5]
-(gauss)	phi1 221.23	Phi 26.54	phi2 207.05
-[Grain6]
-(gauss)	phi1 249.81	Phi 61.47	phi2 152.14
-[Grain7]
-(gauss)	phi1 332.45	Phi 99.16	phi2 345.34
-[Grain8]
-(gauss)	phi1 312.27	Phi 118.27	phi2 181.59
-[Grain9]
-(gauss)	phi1 303.10	Phi 48.21	phi2 358.03
-[Grain10]
-(gauss)	phi1 338.26	Phi 48.11	phi2 176.78
-[Grain11]
-(gauss)	phi1 115.17	Phi 56.54	phi2 223.84
-[Grain12]
-(gauss)	phi1 281.04	Phi 97.48	phi2 27.94
-
-<microstructure>
-[Grain1]
-crystallite 1
-(constituent)	phase 1	texture 1	fraction 1.0
-[Grain2]
-crystallite 1
-(constituent)	phase 1	texture 2	fraction 1.0
-[Grain3]
-crystallite 1
-(constituent)	phase 1	texture 3	fraction 1.0
-[Grain4]
-crystallite 1
-(constituent)	phase 1	texture 4	fraction 1.0
-[Grain5]
-crystallite 1
-(constituent)	phase 1	texture 5	fraction 1.0
-[Grain6]
-crystallite 1
-(constituent)	phase 1	texture 6	fraction 1.0
-[Grain7]
-crystallite 1
-(constituent)	phase 2	texture 7	fraction 1.0
-[Grain8]
-crystallite 1
-(constituent)	phase 2	texture 8	fraction 1.0
-[Grain9]
-crystallite 1
-(constituent)	phase 2	texture 9	fraction 1.0
-[Grain10]
-crystallite 1
-(constituent)	phase 2	texture 10	fraction 1.0
-[Grain11]
-crystallite 1
-(constituent)	phase 2	texture 11	fraction 1.0
-[Grain12]
-crystallite 1
-(constituent)	phase 2	texture 12	fraction 1.0
-
-<phase>
-[pheno_fcc]
-elasticity              hooke
-plasticity              phenopowerlaw
-
-(output) orientation    # quaternion
-(output) F              # deformation gradient tensor
-(output) Fe             # elastic deformation gradient tensor
-(output) Fp             # plastic deformation gradient tensor
-(output) P              # first Piola-Kichhoff stress tensor
-(output) Lp             # plastic velocity gradient tensor
-
-
-lattice_structure       fcc
-Nslip                   12   # per family
-Ntwin                    0   # per family
-
-c11                     106.75e9
-c12                     60.41e9
-c44                     28.34e9
-
-gdot0_slip              0.001
-n_slip                  20
-tau0_slip                 31e6 # per family
-tausat_slip               63e6 # per family
-a_slip                  2.25
-h0_slipslip             75e6
-interaction_slipslip    1 1 1.4 1.4 1.4 1.4
-atol_resistance         1
-
-[pheno_bcc]
-elasticity              hooke
-plasticity              phenopowerlaw
-
-(output) orientation    # quaternion
-(output) F              # deformation gradient tensor
-(output) Fe             # elastic deformation gradient tensor
-(output) Fp             # plastic deformation gradient tensor
-(output) P              # first Piola-Kichhoff stress tensor
-(output) Lp             # plastic velocity gradient tensor
-
-
-lattice_structure       bcc
-Nslip                   12   # per family
-
-c11                     106.75e9
-c12                     60.41e9
-c44                     28.34e9
-
-gdot0_slip              0.001
-n_slip                  20
-tau0_slip                 31e6 # per family
-tausat_slip               63e6 # per family
-a_slip                  2.25
-h0_slipslip             75e6
-interaction_slipslip    1 1 1.4 1.4 1.4 1.4
-atol_resistance         1
diff --git a/python/tests/reference/Result/material.yaml b/python/tests/reference/Result/material.yaml
new file mode 100644
index 000000000..31f16b824
--- /dev/null
+++ b/python/tests/reference/Result/material.yaml
@@ -0,0 +1,103 @@
+---
+homogenization:
+  SX:
+    N_constituents: 1
+    mech: {type: none}
+
+phase:
+  pheno_fcc:
+    elasticity: {C_11: 106.75e9, C_12: 60.41e9, C_44: 28.34e9, type: hooke}
+    generic:
+      output: [F, P, F_e, F_p, L_p, O]
+    lattice: fcc
+    plasticity:
+      N_sl: [12]
+      a_sl: 2.25
+      atol_xi: 1.0
+      dot_gamma_0_sl: 0.001
+      h_0_sl_sl: 75e6
+      h_sl_sl: [1, 1, 1.4, 1.4, 1.4, 1.4]
+      n_sl: 20
+      output: [xi_sl]
+      type: phenopowerlaw
+      xi_0_sl: [31e6]
+      xi_inf_sl: [63e6]
+  pheno_bcc:
+    elasticity: {C_11: 106.75e9, C_12: 60.41e9, C_44: 28.34e9, type: hooke}
+    generic:
+      output: [F, P, F_e, F_p, L_p, O]
+    lattice: bcc
+    plasticity:
+      N_sl: [12]
+      a_sl: 2.25
+      atol_xi: 1.0
+      dot_gamma_0_sl: 0.001
+      h_0_sl_sl: 75e6
+      h_sl_sl: [1, 1, 1.4, 1.4, 1.4, 1.4]
+      n_sl: 20
+      output: [xi_sl]
+      type: phenopowerlaw
+      xi_0_sl: [31e6]
+      xi_inf_sl: [63e6]
+
+material:
+  - constituents:
+      - fraction: 1.0
+        O: [0.8229200444892315, 0.5284940239127993, -0.11958598847729246, 0.17086795611292308]
+        phase: pheno_fcc
+    homogenization: SX
+  - constituents:
+      - fraction: 1.0
+        O: [0.029934934533052786, -0.0463822071939717, 0.9983440440417412, 0.01617900728410769]
+        phase: pheno_fcc
+    homogenization: SX
+  - constituents:
+      - fraction: 1.0
+        O: [0.5285808688806949, 0.7326575088838098, 0.4051997815944012, 0.1401013087924221]
+        phase: pheno_fcc
+    homogenization: SX
+  - constituents:
+      - fraction: 1.0
+        O: [0.1839974517790312, 0.49550065903084944, -0.1541415483910751, -0.8347840545305227]
+        phase: pheno_fcc
+    homogenization: SX
+  - constituents:
+      - fraction: 1.0
+        O: [0.8055693100147384, -0.22778497057116814, -0.028331746016454287, 0.5462320075864553]
+        phase: pheno_fcc
+    homogenization: SX
+  - constituents:
+      - fraction: 1.0
+        O: [0.8025842700117737, -0.33640019337884963, -0.3847408071640489, 0.3076815085881779]
+        phase: pheno_fcc
+    homogenization: SX
+  - constituents:
+      - fraction: 1.0
+        O: [0.6048933483394416, 0.7565005822419409, -0.08545681892422426, -0.2334695661144201]
+        phase: pheno_bcc
+    homogenization: SX
+  - constituents:
+      - fraction: 1.0
+        O: [0.2012339360745425, -0.3580127491130033, -0.7798091137625135, 0.47247171400774884]
+        phase: pheno_bcc
+    homogenization: SX
+  - constituents:
+      - fraction: 1.0
+        O: [0.7949688202267222, 0.3623793306926909, -0.18836147613310203, -0.4485819321629098]
+        phase: pheno_bcc
+    homogenization: SX
+  - constituents:
+      - fraction: 1.0
+        O: [0.19733162113429173, -0.06559103894055797, -0.40230149937129567, 0.8915781236183501]
+        phase: pheno_bcc
+    homogenization: SX
+  - constituents:
+      - fraction: 1.0
+        O: [0.8659916384140512, -0.2761459420825848, 0.38479354764225004, -0.1604238964779258]
+        phase: pheno_bcc
+    homogenization: SX
+  - constituents:
+      - fraction: 1.0
+        O: [0.5951846978175659, 0.4476701545571293, -0.6038886363266418, -0.2840160613735736]
+        phase: pheno_bcc
+    homogenization: SX
diff --git a/python/tests/reference/Result/tensionY.load b/python/tests/reference/Result/tensionY.load
deleted file mode 100644
index 9332144d8..000000000
--- a/python/tests/reference/Result/tensionY.load
+++ /dev/null
@@ -1 +0,0 @@
-fdot * 0 0 0 1.0e-3 0  0 0 *  stress  0 * *   * * *   * * 0  time 20  incs 40 freq 4
diff --git a/python/tests/reference/Result/tensionY.yaml b/python/tests/reference/Result/tensionY.yaml
new file mode 100644
index 000000000..eb34e3e47
--- /dev/null
+++ b/python/tests/reference/Result/tensionY.yaml
@@ -0,0 +1,14 @@
+---
+
+step:
+  - discretization:
+      t: 20
+      N: 40
+      f_out: 4
+    mech:
+      dot_F: [x, 0,      0,
+              0, 1.0e-3, 0,
+              0, 0,      x]
+      P: [0, x, x,
+          x, x, x,
+          x, x, 0]
diff --git a/python/tests/test_Result.py b/python/tests/test_Result.py
index 5ef17cd26..fb178e609 100644
--- a/python/tests/test_Result.py
+++ b/python/tests/test_Result.py
@@ -94,11 +94,11 @@ class TestResult:
             default.pick('invalid',True)
 
     def test_add_absolute(self,default):
-        default.add_absolute('Fe')
-        loc = {'Fe':   default.get_dataset_location('Fe'),
-               '|Fe|': default.get_dataset_location('|Fe|')}
-        in_memory = np.abs(default.read_dataset(loc['Fe'],0))
-        in_file   = default.read_dataset(loc['|Fe|'],0)
+        default.add_absolute('F_e')
+        loc = {'F_e':   default.get_dataset_location('F_e'),
+               '|F_e|': default.get_dataset_location('|F_e|')}
+        in_memory = np.abs(default.read_dataset(loc['F_e'],0))
+        in_file   = default.read_dataset(loc['|F_e|'],0)
         assert np.allclose(in_memory,in_file)
 
     @pytest.mark.parametrize('mode',['direct','function'])
@@ -168,8 +168,8 @@ class TestResult:
 
     @pytest.mark.parametrize('d',[[1,0,0],[0,1,0],[0,0,1]])
     def test_add_IPF_color(self,default,d):
-        default.add_IPF_color('orientation',d)
-        loc = {'orientation': default.get_dataset_location('orientation'),
+        default.add_IPF_color('O',d)
+        loc = {'orientation': default.get_dataset_location('O'),
                'color':       default.get_dataset_location('IPFcolor_[{} {} {}]'.format(*d))}
         qu = default.read_dataset(loc['orientation']).view(np.double).reshape(-1,4)
         crystal_structure = default.get_crystal_structure()
@@ -209,6 +209,22 @@ class TestResult:
         in_memory = mechanics.Mises_stress(default.read_dataset(loc['sigma'],0)).reshape(-1,1)
         in_file   = default.read_dataset(loc['sigma_vM'],0)
         assert np.allclose(in_memory,in_file)
+    
+    def test_add_Mises_invalid(self,default):
+        default.add_Cauchy('P','F')
+        default.add_calculation('sigma_y','#sigma#',unit='y')
+        default.add_Mises('sigma_y')
+        assert default.get_dataset_location('sigma_y_vM') == []
+
+    def test_add_Mises_stress_strain(self,default):
+        default.add_Cauchy('P','F')
+        default.add_calculation('sigma_y','#sigma#',unit='y')
+        default.add_calculation('sigma_x','#sigma#',unit='x')
+        default.add_Mises('sigma_y',kind='strain')
+        default.add_Mises('sigma_x',kind='stress')
+        loc = {'y' :default.get_dataset_location('sigma_y_vM'),
+               'x' :default.get_dataset_location('sigma_x_vM')}
+        assert not np.allclose(default.read_dataset(loc['y'],0),default.read_dataset(loc['x'],0))
 
     def test_add_norm(self,default):
         default.add_norm('F',1)
@@ -231,8 +247,8 @@ class TestResult:
     @pytest.mark.parametrize('polar',[True,False])
     def test_add_pole(self,default,polar):
         pole = np.array([1.,0.,0.])
-        default.add_pole('orientation',pole,polar)
-        loc = {'orientation': default.get_dataset_location('orientation'),
+        default.add_pole('O',pole,polar)
+        loc = {'orientation': default.get_dataset_location('O'),
                'pole':        default.get_dataset_location('p^{}_[1 0 0)'.format(u'rφ' if polar else 'xy'))}
         rot = Rotation(default.read_dataset(loc['orientation']).view(np.double))
         rotated_pole = rot * np.broadcast_to(pole,rot.shape+(3,))
@@ -296,7 +312,11 @@ class TestResult:
         default.add_Cauchy()
         loc = default.get_dataset_location('sigma')
         with h5py.File(default.fname,'r') as f:
-            created_first = f[loc[0]].attrs['Created'].decode()
+            # h5py3 compatibility
+            try:
+                created_first = f[loc[0]].attrs['Created'].decode()
+            except AttributeError:
+                created_first = f[loc[0]].attrs['Created']
         created_first = datetime.strptime(created_first,'%Y-%m-%d %H:%M:%S%z')
 
         if overwrite == 'on':
@@ -305,9 +325,16 @@ class TestResult:
             default.disallow_modification()
 
         time.sleep(2.)
-        default.add_calculation('sigma','#sigma#*0.0+311.','not the Cauchy stress')
+        try:
+            default.add_calculation('sigma','#sigma#*0.0+311.','not the Cauchy stress')
+        except ValueError:
+            pass
         with h5py.File(default.fname,'r') as f:
-            created_second = f[loc[0]].attrs['Created'].decode()
+            # h5py3 compatibility
+            try:
+                created_second = f[loc[0]].attrs['Created'].decode()
+            except AttributeError:
+                created_second = f[loc[0]].attrs['Created']
         created_second = datetime.strptime(created_second,'%Y-%m-%d %H:%M:%S%z')
         if overwrite == 'on':
             assert created_first < created_second and np.allclose(default.read_dataset(loc),311.)
diff --git a/python/tests/test_VTK.py b/python/tests/test_VTK.py
index 63adb6454..bab6051b0 100644
--- a/python/tests/test_VTK.py
+++ b/python/tests/test_VTK.py
@@ -85,6 +85,12 @@ class TestVTK:
         assert(False)
 
 
+    @pytest.mark.parametrize('fname',['a','a.vtp','a.b','a.b.vtp'])
+    def test_filename_variations(self,tmp_path,fname):
+        points = np.random.rand(102,3)
+        v = VTK.from_poly_data(points)
+        v.save(tmp_path/fname)
+
     @pytest.mark.parametrize('name,dataset_type',[('this_file_does_not_exist.vtk', None),
                                                   ('this_file_does_not_exist.vtk','vtk'),
                                                   ('this_file_does_not_exist.vtx', None)])
@@ -92,9 +98,10 @@ class TestVTK:
         with pytest.raises(TypeError):
             VTK.load(name,dataset_type)
 
-    def test_invalid_extension_write(self,default):
-        with pytest.raises(ValueError):
-            default.save('default.txt')
+    def test_add_extension(self,tmp_path,default):
+        default.save(tmp_path/'default.txt',parallel=False)
+        assert os.path.isfile(tmp_path/'default.txt.vtr')
+
 
     def test_invalid_get(self,default):
         with pytest.raises(ValueError):
diff --git a/src/HDF5_utilities.f90 b/src/HDF5_utilities.f90
index a13ac1a8a..4084b2325 100644
--- a/src/HDF5_utilities.f90
+++ b/src/HDF5_utilities.f90
@@ -296,6 +296,8 @@ subroutine HDF5_addAttribute_str(loc_id,attrLabel,attrValue,path)
   logical        :: attrExists
   integer        :: hdferr
   character(len=:), allocatable :: p
+  character(len=:,kind=C_CHAR), allocatable,target :: attrValue_
+  type(c_ptr), target, dimension(1) :: ptr
 
   if (present(path)) then
     p = trim(path)
@@ -303,21 +305,22 @@ subroutine HDF5_addAttribute_str(loc_id,attrLabel,attrValue,path)
     p = '.'
   endif
 
+  attrValue_ = trim(attrValue)//C_NULL_CHAR
+  ptr(1) = c_loc(attrValue_)
+
   call h5screate_f(H5S_SCALAR_F,space_id,hdferr)
   if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_str: h5screate_f')
-  call h5tcopy_f(H5T_NATIVE_CHARACTER, type_id, hdferr)
+  call h5tcopy_f(H5T_STRING, type_id, hdferr)
   if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_str: h5tcopy_f')
-  call h5tset_size_f(type_id, int(len_trim(attrValue),HSIZE_T), hdferr)
-  if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_str: h5tset_size_f')
   call h5aexists_by_name_f(loc_id,trim(p),attrLabel,attrExists,hdferr)
   if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_str: h5aexists_by_name_f')
   if (attrExists) then
-    call h5adelete_by_name_f(loc_id, trim(p), attrLabel, hdferr)
-    if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_str: h5adelete_by_name_f')
+  call h5adelete_by_name_f(loc_id, trim(p), attrLabel, hdferr)
+  if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_str: h5adelete_by_name_f')
   endif
   call h5acreate_by_name_f(loc_id,trim(p),trim(attrLabel),type_id,space_id,attr_id,hdferr)
   if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_str: h5acreate_f')
-  call h5awrite_f(attr_id, type_id, trim(attrValue), int([1],HSIZE_T), hdferr)
+  call h5awrite_f(attr_id, type_id, c_loc(ptr(1)), hdferr)
   if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_str: h5awrite_f')
   call h5aclose_f(attr_id,hdferr)
   if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_str: h5aclose_f')
@@ -436,7 +439,7 @@ subroutine HDF5_addAttribute_int_array(loc_id,attrLabel,attrValue,path)
   array_size = size(attrValue,kind=HSIZE_T)
 
   call h5screate_simple_f(1, array_size, space_id, hdferr, array_size)
-  if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_int_array: h5screate_f')
+  if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_int_array: h5screate_simple_f')
   call h5aexists_by_name_f(loc_id,trim(p),attrLabel,attrExists,hdferr)
   if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_int_array: h5aexists_by_name_f')
   if (attrExists) then
@@ -480,7 +483,7 @@ subroutine HDF5_addAttribute_real_array(loc_id,attrLabel,attrValue,path)
   array_size = size(attrValue,kind=HSIZE_T)
 
   call h5screate_simple_f(1, array_size, space_id, hdferr, array_size)
-  if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_int_array: h5screate_f')
+  if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_int_array: h5screate_simple_f')
   call h5aexists_by_name_f(loc_id,trim(p),attrLabel,attrExists,hdferr)
   if (hdferr < 0) call IO_error(1,ext_msg='HDF5_addAttribute_int_array: h5aexists_by_name_f')
   if (attrExists) then
diff --git a/src/crystallite.f90 b/src/crystallite.f90
index 177fe6cc1..2315fcd77 100644
--- a/src/crystallite.f90
+++ b/src/crystallite.f90
@@ -736,7 +736,7 @@ subroutine crystallite_results
   integer :: p,o
   real(pReal),    allocatable, dimension(:,:,:) :: selected_tensors
   type(rotation), allocatable, dimension(:)     :: selected_rotations
-  character(len=pStringLen)                     :: group,structureLabel
+  character(len=:), allocatable                 :: group,structureLabel
 
   do p=1,size(material_name_phase)
     group = trim('current/constituent')//'/'//trim(material_name_phase(p))//'/generic'
diff --git a/src/homogenization.f90 b/src/homogenization.f90
index 02f1d3bf0..33af8ff95 100644
--- a/src/homogenization.f90
+++ b/src/homogenization.f90
@@ -529,7 +529,7 @@ subroutine homogenization_results
     material_homogenization_type => homogenization_type
 
   integer :: p
-  character(len=pStringLen) :: group_base,group
+  character(len=:), allocatable :: group_base,group
 
   !real(pReal), dimension(:,:,:), allocatable :: temp