Axis for case ibrav=-13 aligned to what is typically found in the literature

CPV/Doc/INPUT_CP.def

@@ -426,10 +426,12 @@ input_description -distribution {Quantum Espresso} -package CP -program cp.x {
               -13          Monoclinic base-centered        celldm(2)=b/a
                            (unique axis b)                 celldm(3)=c/a,
                                                            celldm(5)=cos(beta)
-                    v1 = (  a/2,      -b/2,             0),
-                    v2 = (  a/2,       b/2,             0),
+                    v1 = (  a/2,       b/2,             0),
+                    v2 = ( -a/2,       b/2,             0),
                     v3 = (c*cos(beta),   0,   c*sin(beta)),
                     where beta=angle between axis a and c projected on xz plane
+               IMPORTANT NOTICE: until QE v.6.4.1, axis for ibrav=-13 had a 
+               different definition: v1(old) = v2(now), v2(old) = -v1(now)
 
                14          Triclinic                       celldm(2)= b/a,
                                                            celldm(3)= c/a,

Doc/developer_man.tex

@@ -1349,7 +1349,7 @@ Development can proceed in different ways:
 \item Via ``merge'' requests from a branch of the q-e repository
       ({\em not recommended})
 \item Directly into the ``develop'' branch, or in a ``backport'' branch
-  if existing.
+	if existing ({\em strongly discouraged}).
 \end{enumerate}
 The first option is the recommended one. To start:
 \begin{itemize}

Doc/release-notes

@@ -35,6 +35,9 @@ Problems fixed in development branch :
     they were not broadcasted.
 
 Incompatible changes in development branch :
+  * ibrav=-13 crystal axis converted to a more standard orientation.
+    Atomic positions in crystal axis for the previous convention can
+    be converted by applying the transformation (x,y,z) => (y,-x,z)
   * Initialization has been reorganized, so some initialization routines
     do not perform exactly the same operations as before - should have no
     consequences for codes calling "read_file" to start the calculation,

Modules/latgen.f90

@@ -323,6 +323,7 @@ SUBROUTINE latgen(ibrav,celldm,a1,a2,a3,omega)
      a3(1) = a1(1)
      a3(3) =-a1(3)
   ELSEIF (ibrav == -13) THEN
+     CALL infomsg('latgen','BEWARE: axis for ibrav=-13 changed, see documentation!')
      !
      !     One face centered monoclinic lattice unique axis b
      !
@@ -332,9 +333,9 @@ SUBROUTINE latgen(ibrav,celldm,a1,a2,a3,omega)
      !
      sen = sqrt( 1.d0 - celldm(5) ** 2 )
      a1(1) = 0.5d0 * celldm(1)
-     a1(2) =-a1(1) * celldm(2)
-     a2(1) = a1(1)
-     a2(2) =-a1(2)
+     a1(2) = a1(1) * celldm(2)
+     a2(1) =-a1(1)
+     a2(2) = a1(2)
      a3(1) = celldm(1) * celldm(3) * celldm(5)
      a3(3) = celldm(1) * celldm(3) * sen
      !

Modules/wyckoff.f90

@@ -243,8 +243,8 @@ END SUBROUTINE clean_spacegroup
             tmpx=outco(1,i,k)
             tmpy=outco(2,i,k)
       
-            outco(1,i,k)=tmpx-tmpy
-            outco(2,i,k)=tmpy+tmpx
+            outco(1,i,k)=tmpx+tmpy
+            outco(2,i,k)=tmpy-tmpx
          END DO
       END DO
       

PW/Doc/INPUT_PW.def

@@ -578,10 +578,12 @@ input_description -distribution {Quantum Espresso} -package PWscf -program pw.x
               -13          Monoclinic base-centered        celldm(2)=b/a
                            (unique axis b)                 celldm(3)=c/a,
                                                            celldm(5)=cos(beta)
-                    v1 = (  a/2,      -b/2,             0),
-                    v2 = (  a/2,       b/2,             0),
+                    v1 = (  a/2,       b/2,             0),
+                    v2 = ( -a/2,       b/2,             0),
                     v3 = (c*cos(beta),   0,   c*sin(beta)),
                     where beta=angle between axis a and c projected on xz plane
+               IMPORTANT NOTICE: until QE v.6.4.1, axis for ibrav=-13 had a 
+               different definition: v1(old) = v2(now), v2(old) = -v1(now)
 
                14          Triclinic                       celldm(2)= b/a,
                                                            celldm(3)= c/a,