Merge pull request #13945 from mantidproject/13924_fix_poldi_fit_peaks2d_crystal_systems

PoldiFitPeaks2D should use hexagonal lattice in Pawley fit for trigonal structures in hexagonal setting

Framework/SINQ/inc/MantidSINQ/PoldiFitPeaks2D.h

@@ -6,6 +6,7 @@
 #include "MantidAPI/Algorithm.h"
 #include "MantidAPI/IFunction.h"
 #include "MantidAPI/IPeakFunction.h"
+#include "MantidGeometry/Crystal/PointGroup.h"
 
 #include "MantidKernel/Matrix.h"
 
@@ -104,6 +105,9 @@ protected:
   getFunctionPawley(std::string profileFunctionName,
                     const PoldiPeakCollection_sptr &peakCollection);
 
+  std::string getCrystalSystemFromPointGroup(
+      const Geometry::PointGroup_sptr &pointGroup) const;
+
   std::string
   getRefinedStartingCell(const std::string &initialCell,
                          const std::string &crystalSystem,

Framework/SINQ/src/PoldiFitPeaks2D.cpp

@@ -546,8 +546,7 @@ Poldi2DFunction_sptr PoldiFitPeaks2D::getFunctionPawley(
                                 "peaks do not have point group.");
   }
 
-  std::string crystalSystem =
-      getCrystalSystemAsString(pointGroup->crystalSystem());
+  std::string crystalSystem = getCrystalSystemFromPointGroup(pointGroup);
   pawleyFunction->setCrystalSystem(crystalSystem);
 
   UnitCell cell = peakCollection->unitCell();
@@ -575,6 +574,35 @@ Poldi2DFunction_sptr PoldiFitPeaks2D::getFunctionPawley(
   return mdFunction;
 }
 
+/**
+ * Returns the crystal system for the specified point group
+ *
+ * This function simply uses Geometry::getCrystalSystemAsString(), except when
+ * the crystal system is trigonal but the point group uses hexagonal axes. In
+ * that case this function returns the string for PointGroup::Hexagonal.
+ *
+ * @param pointGroup :: The point group for which to find the crystal system
+ * @return The crystal system for the point group
+ */
+std::string PoldiFitPeaks2D::getCrystalSystemFromPointGroup(
+    const PointGroup_sptr &pointGroup) const {
+  if (!pointGroup) {
+    throw std::invalid_argument(
+        "Cannot return crystal system for null PointGroup.");
+  }
+
+  PointGroup::CrystalSystem crystalSystem = pointGroup->crystalSystem();
+
+  if (crystalSystem == PointGroup::Trigonal) {
+    if (pointGroup->getCoordinateSystem() ==
+        Group::CoordinateSystem::Hexagonal) {
+      return getCrystalSystemAsString(PointGroup::Hexagonal);
+    }
+  }
+
+  return getCrystalSystemAsString(crystalSystem);
+}
+
 /**
  * Tries to refine the initial cell using the supplied peaks
  *

Framework/SINQ/test/PoldiFitPeaks2DTest.h

@@ -433,6 +433,40 @@ public:
     TS_ASSERT_EQUALS(refinedCell, "5 5 5 90 90 90");
   }
 
+  void testGetCrystalSystemFromPointGroup() {
+    TestablePoldiFitPeaks2D alg;
+
+    auto pgCubic = PointGroupFactory::Instance().createPointGroup("m-3m");
+    TS_ASSERT_EQUALS(alg.getCrystalSystemFromPointGroup(pgCubic), "Cubic");
+
+    auto pgTetra = PointGroupFactory::Instance().createPointGroup("4/mmm");
+    TS_ASSERT_EQUALS(alg.getCrystalSystemFromPointGroup(pgTetra), "Tetragonal");
+
+    auto pgOrtho = PointGroupFactory::Instance().createPointGroup("mmm");
+    TS_ASSERT_EQUALS(alg.getCrystalSystemFromPointGroup(pgOrtho),
+                     "Orthorhombic");
+
+    auto pgMono = PointGroupFactory::Instance().createPointGroup("2/m");
+    TS_ASSERT_EQUALS(alg.getCrystalSystemFromPointGroup(pgMono), "Monoclinic");
+
+    auto pgTric = PointGroupFactory::Instance().createPointGroup("-1");
+    TS_ASSERT_EQUALS(alg.getCrystalSystemFromPointGroup(pgTric), "Triclinic");
+
+    auto pgHex = PointGroupFactory::Instance().createPointGroup("6/mmm");
+    TS_ASSERT_EQUALS(alg.getCrystalSystemFromPointGroup(pgHex), "Hexagonal");
+
+    auto pgTrigRh = PointGroupFactory::Instance().createPointGroup("-3m r");
+    TS_ASSERT_EQUALS(alg.getCrystalSystemFromPointGroup(pgTrigRh), "Trigonal");
+
+    auto pgTrigHex = PointGroupFactory::Instance().createPointGroup("-3m");
+    TS_ASSERT_EQUALS(alg.getCrystalSystemFromPointGroup(pgTrigHex),
+                     "Hexagonal");
+
+    PointGroup_sptr invalid;
+    TS_ASSERT_THROWS(alg.getCrystalSystemFromPointGroup(invalid),
+                     std::invalid_argument);
+  }
+
 private:
   PoldiInstrumentAdapter_sptr m_instrument;
   PoldiTimeTransformer_sptr m_timeTransformer;