addres mfh's comments

src/utils/cells.jl

@@ -39,12 +39,12 @@ Implementation of a computational cell for particle systems
 """
 struct PeriodicCell{D, T}
    cell_vectors::NTuple{D, SVector{D, T}} 
-   pbc::NTuple{D, Bool}
+   periodicity::NTuple{D, Bool}
 end
 
 bounding_box(cell::PeriodicCell) = cell.cell_vectors 
 
-periodicity(cell::PeriodicCell) = cell.pbc
+periodicity(cell::PeriodicCell) = cell.periodicity
 
 n_dimensions(::PeriodicCell{D}) where {D} = D
 
@@ -62,7 +62,7 @@ PeriodicCell(cl::Union{AbstractSystem, PeriodicCell}) =
 
 function Base.show(io::IO, cϵll::PeriodicCell{D}) where {D} 
    u = unit(first(cϵll.cell_vectors[1][1]))
-   print(io, "PeriodicCell(", prod(p -> p ? "T" : "F", cϵll.pbc), ", ")  
+   print(io, "PeriodicCell(", prod(p -> p ? "T" : "F", periodicity(cϵll)), ", ")
    for d = 1:D 
       print(io, ustrip.(cϵll.cell_vectors[d]), u)
       if d < D; print(io, ", "); end 
@@ -78,7 +78,7 @@ end
 # allowed input types that convert automatically to the 
 # intended format for cell vectors,  NTuple{D, SVector{D, T}}
 const AUTOBOX = Union{NTuple{D, <: AbstractVector}, 
-                  AbstractVector{<: AbstractVector}} where {D}
+                      AbstractVector{<: AbstractVector}} where {D}
 
 # allowed input types that convert automatically to the 
 # intended format for pbc,  NTuple{D, Bool}
@@ -105,7 +105,7 @@ _auto_cell_vectors(vecs::AbstractVector{<: AbstractVector}) =
 
 # different ways to construct PBC 
 
-_auto_pbc1(bc::Bool)   = bc 
+_auto_pbc1(pbc::Bool)  = pbc 
 _auto_pbc1(::Nothing)  = false 
 
 _auto_pbc(bc::Tuple, cell_vectors = nothing) =