diff --git a/regressioncheck/CHE_poisson/SurfFlux_ThermionicEmission_Schottky/parameter.ini b/regressioncheck/CHE_poisson/SurfFlux_ThermionicEmission_Schottky/parameter.ini
index 5f25f34a2..d04cc4703 100644
--- a/regressioncheck/CHE_poisson/SurfFlux_ThermionicEmission_Schottky/parameter.ini
+++ b/regressioncheck/CHE_poisson/SurfFlux_ThermionicEmission_Schottky/parameter.ini
@@ -87,7 +87,7 @@ BPO-Species                = (/1/)   ! electrons
 ! =============================================================================== !
 Part-Species1-MassIC              = 9.11E-31
 Part-Species1-ChargeIC            = -1.60217653E-19
-Part-Species1-MacroParticleFactor = 2E4
+Part-Species1-MacroParticleFactor = 1E4
 
 Part-Species1-nSurfaceFluxBCs=1
 Part-Species1-Surfaceflux1-BC=2
diff --git a/src/particles/boundary/particle_boundary_init.f90 b/src/particles/boundary/particle_boundary_init.f90
index 51bab910c..460a0db9d 100644
--- a/src/particles/boundary/particle_boundary_init.f90
+++ b/src/particles/boundary/particle_boundary_init.f90
@@ -209,6 +209,10 @@ SUBROUTINE InitializeVariablesPartBoundary()
 PartBound%TargetBoundCond = -1
 ALLOCATE(PartBound%MomentumACC(      1:nPartBound))
 PartBound%MomentumACC = -1
+ALLOCATE(PartBound%OnlySpecular(     1:nPartBound))
+PartBound%OnlySpecular = .FALSE.
+ALLOCATE(PartBound%OnlyDiffuse(      1:nPartBound))
+PartBound%OnlyDiffuse = .FALSE.
 ALLOCATE(PartBound%WallTemp(         1:nPartBound))
 PartBound%WallTemp = -1.
 ALLOCATE(PartBound%WallTemp2(        1:nPartBound))
@@ -299,6 +303,11 @@ SUBROUTINE InitializeVariablesPartBoundary()
 #endif
     PartBound%TargetBoundCond(iPartBound) = PartBound%ReflectiveBC
     PartBound%MomentumACC(iPartBound)     = GETREAL('Part-Boundary'//TRIM(hilf)//'-MomentumACC')
+    IF(PartBound%MomentumACC(iPartBound).EQ.0.0) THEN
+      PartBound%OnlySpecular(iPartBound) = .TRUE.
+    ELSE IF(PartBound%MomentumACC(iPartBound).EQ.1.0) THEN
+      PartBound%OnlyDiffuse(iPartBound)  = .TRUE.
+    END IF
     PartBound%WallTemp(iPartBound)        = GETREAL('Part-Boundary'//TRIM(hilf)//'-WallTemp')
     PartBound%TransACC(iPartBound)        = GETREAL('Part-Boundary'//TRIM(hilf)//'-TransACC')
     PartBound%VibACC(iPartBound)          = GETREAL('Part-Boundary'//TRIM(hilf)//'-VibACC')
@@ -1122,6 +1131,8 @@ SUBROUTINE FinalizeParticleBoundary()
 SDEALLOCATE(PartBound%SourceBoundName)
 SDEALLOCATE(PartBound%TargetBoundCond)
 SDEALLOCATE(PartBound%MomentumACC)
+SDEALLOCATE(PartBound%OnlySpecular)
+SDEALLOCATE(PartBound%OnlyDiffuse)
 SDEALLOCATE(PartBound%WallTemp)
 SDEALLOCATE(PartBound%WallTemp2)
 SDEALLOCATE(PartBound%WallTempDelta)
diff --git a/src/particles/boundary/particle_boundary_vars.f90 b/src/particles/boundary/particle_boundary_vars.f90
index c09697f27..0ddad36a7 100644
--- a/src/particles/boundary/particle_boundary_vars.f90
+++ b/src/particles/boundary/particle_boundary_vars.f90
@@ -257,6 +257,8 @@ MODULE MOD_Particle_Boundary_Vars
   INTEGER              , ALLOCATABLE     :: MapToFieldBC(:)             ! Map from Particle BC (NOT TO TYPE!) to PICLas BCindex
   !!INTEGER              , ALLOCATABLE     :: SideBCType(:)            ! list with boundary condition for each side
   REAL    , ALLOCATABLE                  :: MomentumACC(:)
+  LOGICAL , ALLOCATABLE                  :: OnlySpecular(:)
+  LOGICAL , ALLOCATABLE                  :: OnlyDiffuse(:)
   REAL    , ALLOCATABLE                  :: WallTemp(:), WallTemp2(:), WallTempDelta(:)
   REAL    , ALLOCATABLE                  :: TempGradStart(:,:), TempGradEnd(:,:), TempGradVec(:,:)
   REAL    , ALLOCATABLE                  :: TransACC(:)
diff --git a/src/particles/dsmc/dsmc_symmetry.f90 b/src/particles/dsmc/dsmc_symmetry.f90
index ccfeec989..d4f9997b9 100644
--- a/src/particles/dsmc/dsmc_symmetry.f90
+++ b/src/particles/dsmc/dsmc_symmetry.f90
@@ -84,15 +84,16 @@ SUBROUTINE DSMC_2D_InitVolumes()
 USE MOD_Particle_Mesh_Vars      ,ONLY: GEO,LocalVolume,MeshVolume
 USE MOD_DSMC_Vars               ,ONLY: SymmetrySide
 USE MOD_Particle_Mesh_Vars      ,ONLY: ElemVolume_Shared,ElemCharLength_Shared
-USE MOD_Particle_Mesh_Vars      ,ONLY: NodeCoords_Shared,ElemSideNodeID_Shared, SideInfo_Shared
+USE MOD_Particle_Mesh_Vars      ,ONLY: NodeCoords_Shared,ElemSideNodeID_Shared, SideInfo_Shared, SideIsSymSide_Shared
 USE MOD_Mesh_Tools              ,ONLY: GetCNElemID
+USE MOD_Particle_Mesh_Vars      ,ONLY: nNonUniqueGlobalSides
 USE MOD_Particle_Mesh_Tools     ,ONLY: GetGlobalNonUniqueSideID
 USE MOD_Particle_Surfaces       ,ONLY: CalcNormAndTangTriangle
 #if USE_MPI
-USE MOD_MPI_Shared              ,ONLY: BARRIER_AND_SYNC
+USE MOD_MPI_Shared
 USE MOD_MPI_Shared_Vars         ,ONLY: MPI_COMM_SHARED
 USE MOD_Particle_Mesh_Vars      ,ONLY: offsetComputeNodeElem
-USE MOD_Particle_Mesh_Vars      ,ONLY: ElemVolume_Shared_Win,ElemCharLength_Shared_Win
+USE MOD_Particle_Mesh_Vars      ,ONLY: ElemVolume_Shared_Win,ElemCharLength_Shared_Win,SideIsSymSide_Shared_Win
 USE MOD_MPI_Shared_Vars         ,ONLY: myComputeNodeRank,MPI_COMM_LEADERS_SHARED
 #endif /*USE_MPI*/
 ! IMPLICIT VARIABLE HANDLING
@@ -113,13 +114,14 @@ SUBROUTINE DSMC_2D_InitVolumes()
 !===================================================================================================================================
 
 #if USE_MPI
-FirstElem = offsetElem - offsetComputeNodeElem + 1
-LastElem  = offsetElem - offsetComputeNodeElem + nElems
+CALL Allocate_Shared((/nNonUniqueGlobalSides/),SideIsSymSide_Shared_Win,SideIsSymSide_Shared)
+CALL MPI_WIN_LOCK_ALL(0,SideIsSymSide_Shared_Win,IERROR)
 #else
-firstElem = 1
-lastElem  = nElems
+ALLOCATE(SideIsSymSide_Shared(nNonUniqueGlobalSides))
 #endif  /*USE_MPI*/
 
+SideIsSymSide_Shared = .FALSE.
+
 SymmetryBCExists = .FALSE.
 ALLOCATE(SymmetrySide(1:nElems,1:2))                ! 1: GlobalSide, 2: LocalSide
 SymmetrySide = -1
@@ -137,6 +139,8 @@ SUBROUTINE DSMC_2D_InitVolumes()
   iLocSide = SideToElem(S2E_LOC_SIDE_ID,BCSideID)
   SideID=GetGlobalNonUniqueSideID(offsetElem+locElemID,iLocSide)
   IF (PartBound%TargetBoundCond(PartBound%MapToPartBC(SideInfo_Shared(SIDE_BCID,SideID))).EQ.PartBound%SymmetryBC) THEN
+    ! Mark side to skip in tracking
+    SideIsSymSide_Shared(SideID) = .TRUE.
     CNElemID = GetCNElemID(SideInfo_Shared(SIDE_ELEMID,SideID))
     iLocSide = SideInfo_Shared(SIDE_LOCALID,SideID)
     ! Exclude the symmetry axis (y=0)
@@ -177,14 +181,25 @@ SUBROUTINE DSMC_2D_InitVolumes()
   END IF
 END DO
 
+
 IF(.NOT.SymmetryBCExists) THEN
   CALL abort(__STAMP__&
     ,'At least one symmetric BC (in the xy-plane) has to be defined for 2D simulations')
 END IF
 
 ! LocalVolume & MeshVolume: Recalculate the volume of the mesh of a single process and the total mesh volume
+#if USE_MPI
+FirstElem = offsetElem - offsetComputeNodeElem + 1
+LastElem  = offsetElem - offsetComputeNodeElem + nElems
+#else
+firstElem = 1
+lastElem  = nElems
+#endif  /*USE_MPI*/
+
 LocalVolume = SUM(ElemVolume_Shared(FirstElem:LastElem))
+
 #if USE_MPI
+CALL BARRIER_AND_SYNC(SideIsSymSide_Shared_Win ,MPI_COMM_SHARED)
 CALL BARRIER_AND_SYNC(ElemVolume_Shared_Win    ,MPI_COMM_SHARED)
 CALL BARRIER_AND_SYNC(ElemCharLength_Shared_Win,MPI_COMM_SHARED)
 ! Compute-node mesh volume
diff --git a/src/particles/particle_mesh/particle_mesh_readin.f90 b/src/particles/particle_mesh/particle_mesh_readin.f90
index 0ace4a412..4ad065c6d 100644
--- a/src/particles/particle_mesh/particle_mesh_readin.f90
+++ b/src/particles/particle_mesh/particle_mesh_readin.f90
@@ -465,6 +465,7 @@ SUBROUTINE FinalizeMeshReadin()
 #endif /*USE_MPI*/
 
 ! Then, free the pointers or arrays
+ADEALLOCATE(SideIsSymSide_Shared)
 ADEALLOCATE(ElemVolume_Shared)
 ADEALLOCATE(ElemCharLength_Shared)
 
diff --git a/src/particles/particle_mesh/particle_mesh_vars.f90 b/src/particles/particle_mesh/particle_mesh_vars.f90
index b6b03604d..9ff537165 100644
--- a/src/particles/particle_mesh/particle_mesh_vars.f90
+++ b/src/particles/particle_mesh/particle_mesh_vars.f90
@@ -169,8 +169,10 @@ MODULE MOD_Particle_Mesh_Vars
 REAL,ALLOCPOINT    :: ElemCharLengthX_Shared(:)
 REAL,ALLOCPOINT    :: ElemCharLengthY_Shared(:)
 REAL,ALLOCPOINT    :: ElemCharLengthZ_Shared(:)
+LOGICAL,ALLOCPOINT :: SideIsSymSide_Shared(:)
 
 #if USE_MPI
+INTEGER            :: SideIsSymSide_Shared_Win
 ! integers to hold shared memory windows
 INTEGER         :: NodeToElemMapping_Shared_Win
 INTEGER         :: NodeToElemInfo_Shared_Win
diff --git a/src/particles/surfacemodel/surfacemodel_main.f90 b/src/particles/surfacemodel/surfacemodel_main.f90
index cd8abe045..e690b7ee0 100644
--- a/src/particles/surfacemodel/surfacemodel_main.f90
+++ b/src/particles/surfacemodel/surfacemodel_main.f90
@@ -287,18 +287,18 @@ SUBROUTINE MaxwellScattering(PartID,SideID,n_loc,SpecularReflectionOnly_opt)
 ACC = PartBound%MomentumACC(iBC)
 
 ! Check if optional parameter was supplied
-ASSOCIATE( SpecularReflectionOnly => MERGE(SpecularReflectionOnly_opt, .FALSE., PRESENT(SpecularReflectionOnly_opt)) ) 
-  IF (SpecularReflectionOnly.OR.ACC.EQ.0.0) THEN
+ASSOCIATE( SpecularReflectionOnly => MERGE(SpecularReflectionOnly_opt,PartBound%OnlySpecular(iBC),PRESENT(SpecularReflectionOnly_opt)))
+  IF (SpecularReflectionOnly) THEN
     CALL PerfectReflection(PartID,SideID,n_loc)
-  ELSE IF(ACC.LT.1.0) THEN
+  ELSE IF(PartBound%OnlyDiffuse(iBC)) THEN
+    CALL DiffuseReflection(PartID,SideID,n_loc)
+  ELSE
     CALL RANDOM_NUMBER(RanNum)
     IF(RanNum.GE.ACC) THEN
       CALL PerfectReflection(PartID,SideID,n_loc)
     ELSE
       CALL DiffuseReflection(PartID,SideID,n_loc)
     END IF
-  ELSE
-    CALL DiffuseReflection(PartID,SideID,n_loc)
   END IF
 END ASSOCIATE
 
diff --git a/src/particles/tracking/particle_triatracking.f90 b/src/particles/tracking/particle_triatracking.f90
index c95ddb6ba..90be606e9 100644
--- a/src/particles/tracking/particle_triatracking.f90
+++ b/src/particles/tracking/particle_triatracking.f90
@@ -54,6 +54,7 @@ SUBROUTINE ParticleTriaTracking()
 USE MOD_Mesh_Tools                  ,ONLY: GetCNElemID
 USE MOD_Particle_Vars               ,ONLY: PEM,PDM,PartSpecies
 USE MOD_Particle_Vars               ,ONLY: PartState,LastPartPos
+USE MOD_Particle_Vars               ,ONLY: Symmetry
 USE MOD_Particle_Mesh_Tools         ,ONLY: ParticleInsideQuad3D
 USE MOD_Particle_Mesh_Vars
 USE MOD_Particle_Tracking_vars      ,ONLY: ntracks,MeasureTrackTime,CountNbrOfLostParts, NbrOfLostParticles, TrackInfo
@@ -154,6 +155,10 @@ SUBROUTINE ParticleTriaTracking()
         nlocSides = ElemInfo_Shared(ELEM_LASTSIDEIND,ElemID) -  ElemInfo_Shared(ELEM_FIRSTSIDEIND,ElemID)
         DO iLocSide=1,nlocSides
           TempSideID = ElemInfo_Shared(ELEM_FIRSTSIDEIND,ElemID) + iLocSide
+          ! Skip symmetry side
+          IF(Symmetry%Order.EQ.2) THEN
+            IF(SideIsSymSide_Shared(TempSideID)) CYCLE
+          END IF
           localSideID = SideInfo_Shared(SIDE_LOCALID,TempSideID)
 
           ! Side is not one of the 6 local sides