diff --git a/regtest/multicolvar/rt-axis-angles/Makefile b/regtest/multicolvar/rt-axis-angles/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..3703b27cea227aa053fb6d1d73f861e4384dbcee
--- /dev/null
+++ b/regtest/multicolvar/rt-axis-angles/Makefile
@@ -0,0 +1 @@
+include ../../scripts/test.make
diff --git a/regtest/multicolvar/rt-axis-angles/colvar.reference b/regtest/multicolvar/rt-axis-angles/colvar.reference
new file mode 100644
index 0000000000000000000000000000000000000000..33f854f1e82ea21c18e705ea276b3f060a46331d
--- /dev/null
+++ b/regtest/multicolvar/rt-axis-angles/colvar.reference
@@ -0,0 +1,6 @@
+#! FIELDS time dx.lessthan dy.between
+ 0.000000 1.4487 0.7038
+ 0.050000 1.4590 0.7042
+ 0.100000 1.4215 0.9236
+ 0.150000 1.3815 0.9333
+ 0.200000 1.3622 0.9406
diff --git a/regtest/multicolvar/rt-axis-angles/config b/regtest/multicolvar/rt-axis-angles/config
new file mode 100644
index 0000000000000000000000000000000000000000..4804b7f2a86c1dcb06f52d08f8dff331e318192f
--- /dev/null
+++ b/regtest/multicolvar/rt-axis-angles/config
@@ -0,0 +1,4 @@
+type=driver
+# this is to test a different name
+arg="--plumed plumed.dat --trajectory-stride 10 --timestep 0.005 --ixyz trajectory.xyz --dump-forces forces --dump-forces-fmt=%8.4f"
+extra_files="../../trajectories/trajectory.xyz"
diff --git a/regtest/multicolvar/rt-axis-angles/deriv.reference b/regtest/multicolvar/rt-axis-angles/deriv.reference
new file mode 100644
index 0000000000000000000000000000000000000000..7f999b078ff85132578d0b5d09670ac9abb805e6
--- /dev/null
+++ b/regtest/multicolvar/rt-axis-angles/deriv.reference
@@ -0,0 +1,106 @@
+#! FIELDS time parameter dx.lessthan dy.between
+ 0.000000 0 -0.0531 0.0021
+ 0.000000 1 -0.0009 0.1631
+ 0.000000 2 0.0602 0.0000
+ 0.000000 3 0.0531 -0.0021
+ 0.000000 4 0.0009 -0.1631
+ 0.000000 5 -0.0602 0.0000
+ 0.000000 6 -0.8154 -0.1562
+ 0.000000 7 0.0183 0.0068
+ 0.000000 8 -0.0178 0.0000
+ 0.000000 9 0.8154 0.1562
+ 0.000000 10 -0.0183 -0.0068
+ 0.000000 11 0.0178 0.0000
+ 0.000000 12 -0.0806 -0.0038
+ 0.000000 13 -0.0002 0.1547
+ 0.000000 14 0.0563 0.0000
+ 0.000000 15 -0.6937 -0.1331
+ 0.000000 16 0.0156 0.0038
+ 0.000000 17 -0.0159 0.0000
+ 0.000000 18 0.6294 0.1308
+ 0.000000 19 -0.0159 0.1306
+ 0.000000 20 0.0650 0.0000
+ 0.050000 0 -0.0357 0.0012
+ 0.050000 1 -0.0004 0.1507
+ 0.050000 2 0.0442 0.0000
+ 0.050000 3 0.0357 -0.0012
+ 0.050000 4 0.0004 -0.1507
+ 0.050000 5 -0.0442 0.0000
+ 0.050000 6 -0.8378 -0.1609
+ 0.050000 7 0.0227 0.0086
+ 0.050000 8 -0.0223 0.0000
+ 0.050000 9 0.8378 0.1609
+ 0.050000 10 -0.0227 -0.0086
+ 0.050000 11 0.0223 0.0000
+ 0.050000 12 -0.0735 -0.0059
+ 0.050000 13 0.0006 0.1549
+ 0.050000 14 0.0443 0.0000
+ 0.050000 15 -0.6936 -0.1333
+ 0.050000 16 0.0188 0.0059
+ 0.050000 17 -0.0188 0.0000
+ 0.050000 18 0.6526 0.1320
+ 0.050000 19 -0.0188 0.1178
+ 0.050000 20 0.0547 0.0000
+ 0.100000 0 -0.0278 0.0011
+ 0.100000 1 -0.0004 0.1401
+ 0.100000 2 0.0361 0.0000
+ 0.100000 3 0.0278 -0.0011
+ 0.100000 4 0.0004 -0.1401
+ 0.100000 5 -0.0361 0.0000
+ 0.100000 6 -0.8591 0.2132
+ 0.100000 7 -0.0017 0.0009
+ 0.100000 8 0.0018 0.0000
+ 0.100000 9 0.8591 -0.2132
+ 0.100000 10 0.0017 -0.0009
+ 0.100000 11 -0.0018 0.0000
+ 0.100000 12 -0.0280 0.0005
+ 0.100000 13 -0.0004 0.1545
+ 0.100000 14 0.0398 0.0000
+ 0.100000 15 -0.6276 0.1558
+ 0.100000 16 -0.0012 -0.0005
+ 0.100000 17 0.0010 0.0000
+ 0.100000 18 0.6675 -0.1706
+ 0.100000 19 0.0010 0.1184
+ 0.100000 20 0.0292 0.0000
+ 0.150000 0 -0.0233 -0.0006
+ 0.150000 1 0.0002 0.1311
+ 0.150000 2 0.0311 0.0000
+ 0.150000 3 0.0233 0.0006
+ 0.150000 4 -0.0002 -0.1311
+ 0.150000 5 -0.0311 0.0000
+ 0.150000 6 -0.8413 0.2435
+ 0.150000 7 -0.0244 0.0193
+ 0.150000 8 0.0321 0.0000
+ 0.150000 9 0.8413 -0.2435
+ 0.150000 10 0.0244 -0.0193
+ 0.150000 11 -0.0321 0.0000
+ 0.150000 12 0.0146 -0.0128
+ 0.150000 13 0.0014 0.1538
+ 0.150000 14 0.0351 0.0000
+ 0.150000 15 -0.5308 0.1536
+ 0.150000 16 -0.0154 0.0128
+ 0.150000 17 0.0204 0.0000
+ 0.150000 18 0.6788 -0.2029
+ 0.150000 19 0.0204 0.1000
+ 0.150000 20 0.0008 0.0000
+ 0.200000 0 -0.0182 -0.0004
+ 0.200000 1 0.0001 0.1273
+ 0.200000 2 0.0256 0.0000
+ 0.200000 3 0.0182 0.0004
+ 0.200000 4 -0.0001 -0.1273
+ 0.200000 5 -0.0256 0.0000
+ 0.200000 6 -0.7791 0.2441
+ 0.200000 7 -0.0321 0.0307
+ 0.200000 8 0.0460 0.0000
+ 0.200000 9 0.7791 -0.2441
+ 0.200000 10 0.0321 -0.0307
+ 0.200000 11 -0.0460 0.0000
+ 0.200000 12 0.0386 -0.0195
+ 0.200000 13 0.0026 0.1524
+ 0.200000 14 0.0276 0.0000
+ 0.200000 15 -0.4828 0.1513
+ 0.200000 16 -0.0199 0.0195
+ 0.200000 17 0.0286 0.0000
+ 0.200000 18 0.6769 -0.2173
+ 0.200000 19 0.0286 0.0826
+ 0.200000 20 -0.0187 0.0000
diff --git a/regtest/multicolvar/rt-axis-angles/plumed.dat b/regtest/multicolvar/rt-axis-angles/plumed.dat
new file mode 100644
index 0000000000000000000000000000000000000000..ccfbfa42bd528a2c3927e20869319471b7fde4e5
--- /dev/null
+++ b/regtest/multicolvar/rt-axis-angles/plumed.dat
@@ -0,0 +1,7 @@
+dx: XANGLES ATOMS1=1,2 ATOMS2=5,4 LESS_THAN={RATIONAL R_0=1.5}
+#dxn: XANGLES ATOMS1=1,2 ATOMS2=5,4 LESS_THAN={RATIONAL R_0=1.5} NUMERICAL_DERIVATIVES
+dy: ZYTORSIONS ATOMS1=1,2 ATOMS2=5,4 BETWEEN={GAUSSIAN LOWER=-3 UPPER=1.5 SMEAR=0.5}
+#dyn: ZYTORSIONS ATOMS1=1,2 ATOMS2=5,4 BETWEEN={GAUSSIAN LOWER=-3 UPPER=1.5 SMEAR=0.5} NUMERICAL_DERIVATIVES
+PRINT ARG=dx.*,dy.* FILE=colvar FMT=%8.4f
+DUMPDERIVATIVES ARG=dx.*,dy.* FILE=deriv FMT=%8.4f
+
diff --git a/src/multicolvar/XAngle.cpp b/src/multicolvar/XAngle.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..1fb77ef8694f9d2a016bf2b8a6a8beec30769b12
--- /dev/null
+++ b/src/multicolvar/XAngle.cpp
@@ -0,0 +1,170 @@
+/* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Copyright (c) 2012-2016 The plumed team
+ (see the PEOPLE file at the root of the distribution for a list of names)
+
+ See http://www.plumed.org for more information.
+
+ This file is part of plumed, version 2.
+
+ plumed is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ plumed is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with plumed. If not, see <http://www.gnu.org/licenses/>.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
+#include "MultiColvar.h"
+#include "core/ActionRegister.h"
+#include "tools/Angle.h"
+#include "tools/SwitchingFunction.h"
+
+#include <string>
+#include <cmath>
+
+using namespace std;
+
+namespace PLMD{
+namespace multicolvar{
+
+//+PLUMEDOC MCOLVAR XANGLES
+/*
+Calculate the angles between the vector connecting two atoms and the x axis.
+
+\par Examples
+
+The following input tells plumed to calculate the angles between the x-axis and the vector connecting atom 3 to atom 5 and between the x-axis
+and the vector connecting atom 1 to atom 2. The minimum of these two quantities is then
+\verbatim
+XANLGES ATOMS1=3,5 ATOMS2=1,2 MIN={BETA=0.1} LABEL=d1
+PRINT ARG=d1.min
+\endverbatim
+(See also \ref PRINT).
+*/
+//+ENDPLUMEDOC
+
+//+PLUMEDOC MCOLVAR YANGLES
+/*
+Calculate the angles between the vector connecting two atoms and the y axis.
+
+\par Examples
+
+The following input tells plumed to calculate the angles between the y-axis and the vector connecting atom 3 to atom 5 and between the y-axis
+and the vector connecting atom 1 to atom 2. The minimum of these two quantities is then
+\verbatim
+YANLGES ATOMS1=3,5 ATOMS2=1,2 MIN={BETA=0.1} LABEL=d1
+PRINT ARG=d1.min
+\endverbatim
+(See also \ref PRINT).
+*/
+//+ENDPLUMEDOC
+
+//+PLUMEDOC MCOLVAR ZANGLES
+/*
+Calculate the angles between the vector connecting two atoms and the z axis.
+
+\par Examples
+
+The following input tells plumed to calculate the angles between the z-axis and the vector connecting atom 3 to atom 5 and between the z-axis
+and the vector connecting atom 1 to atom 2. The minimum of these two quantities is then
+\verbatim
+ZANLGES ATOMS1=3,5 ATOMS2=1,2 MIN={BETA=0.1} LABEL=d1
+PRINT ARG=d1.min
+\endverbatim
+(See also \ref PRINT).
+*/
+//+ENDPLUMEDOC
+
+
+
+class XAngles : public MultiColvar {
+private:
+ bool use_sf;
+ unsigned myc;
+ SwitchingFunction sf1;
+public:
+ static void registerKeywords( Keywords& keys );
+ explicit XAngles(const ActionOptions&);
+// active methods:
+ virtual double compute( const unsigned& tindex, AtomValuePack& myatoms ) const ;
+ double calculateWeight( const unsigned& taskCode, const double& weight, AtomValuePack& ) const ;
+/// Returns the number of coordinates of the field
+ bool isPeriodic(){ return false; }
+};
+
+PLUMED_REGISTER_ACTION(XAngles,"XANGLES")
+PLUMED_REGISTER_ACTION(XAngles,"YANGLES")
+PLUMED_REGISTER_ACTION(XAngles,"ZANGLES")
+
+void XAngles::registerKeywords( Keywords& keys ){
+ MultiColvar::registerKeywords( keys );
+ keys.use("ATOMS"); keys.use("MAX"); keys.use("ALT_MIN");
+ keys.use("MEAN"); keys.use("MIN"); keys.use("LESS_THAN");
+ keys.use("LOWEST"); keys.use("HIGHEST");
+ keys.use("MORE_THAN"); keys.use("BETWEEN"); keys.use("HISTOGRAM"); keys.use("MOMENTS");
+ keys.add("atoms-1","GROUP","Calculate the distance between each distinct pair of atoms in the group");
+ keys.add("atoms-2","GROUPA","Calculate the distances between all the atoms in GROUPA and all "
+ "the atoms in GROUPB. This must be used in conjuction with GROUPB.");
+ keys.add("atoms-2","GROUPB","Calculate the distances between all the atoms in GROUPA and all the atoms "
+ "in GROUPB. This must be used in conjuction with GROUPA.");
+ keys.add("optional","SWITCH","A switching function that ensures that only angles are only computed when atoms are within "
+ "are within a certain fixed cutoff. The following provides information on the \\ref switchingfunction that are available.");
+}
+
+XAngles::XAngles(const ActionOptions&ao):
+PLUMED_MULTICOLVAR_INIT(ao),
+use_sf(false)
+{
+ if( getName().find("X")!=std::string::npos) myc=0;
+ else if( getName().find("Y")!=std::string::npos) myc=1;
+ else if( getName().find("Z")!=std::string::npos) myc=2;
+ else plumed_error();
+
+ // Read in switching function
+ std::string sfinput, errors; parse("SWITCH",sfinput);
+ if( sfinput.length()>0 ){
+ use_sf=true; weightHasDerivatives=true;
+ sf1.set(sfinput,errors);
+ if( errors.length()!=0 ) error("problem reading SWITCH keyword : " + errors );
+ log.printf(" only calculating angles for atoms separated by less than %s\n", sf1.description().c_str() );
+ setLinkCellCutoff( sf1.get_dmax() );
+ }
+
+ // Read in the atoms
+ std::vector<AtomNumber> all_atoms;
+ readTwoGroups( "GROUP", "GROUPA", "GROUPB", all_atoms );
+ int natoms=2; readAtoms( natoms, all_atoms );
+ // And check everything has been read in correctly
+ checkRead();
+}
+
+double XAngles::calculateWeight( const unsigned& taskCode, const double& weight, AtomValuePack& myatoms ) const {
+ if(!use_sf) return 1.0;
+
+ Vector distance=getSeparation( myatoms.getPosition(0), myatoms.getPosition(1) );
+ double dw, w = sf1.calculateSqr( distance.modulo2(), dw );
+ addAtomDerivatives( 0, 0, (-dw)*distance, myatoms );
+ addAtomDerivatives( 0, 1, (+dw)*distance, myatoms );
+ myatoms.addBoxDerivatives( 0, (-dw)*Tensor(distance,distance) );
+ return w;
+}
+
+double XAngles::compute( const unsigned& tindex, AtomValuePack& myatoms ) const {
+ Vector ddij, ddik, axis, distance; axis.zero(); axis[myc]=1;
+ distance=getSeparation( myatoms.getPosition(0), myatoms.getPosition(1) );
+ PLMD::Angle a; double angle=a.compute( distance, axis, ddij, ddik );
+
+ addAtomDerivatives( 1, 0, -ddij, myatoms );
+ addAtomDerivatives( 1, 1, ddij, myatoms );
+ myatoms.addBoxDerivatives( 1, -Tensor( distance,ddij ) );
+ return angle;
+}
+
+}
+}
+
diff --git a/src/multicolvar/XYTorsion.cpp b/src/multicolvar/XYTorsion.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..67f4f82c267e0460b31fbe7024be61ada704d44c
--- /dev/null
+++ b/src/multicolvar/XYTorsion.cpp
@@ -0,0 +1,226 @@
+/* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Copyright (c) 2012-2016 The plumed team
+ (see the PEOPLE file at the root of the distribution for a list of names)
+
+ See http://www.plumed.org for more information.
+
+ This file is part of plumed, version 2.
+
+ plumed is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ plumed is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with plumed. If not, see <http://www.gnu.org/licenses/>.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
+#include "MultiColvar.h"
+#include "core/ActionRegister.h"
+#include "tools/Torsion.h"
+#include "tools/SwitchingFunction.h"
+
+#include <string>
+#include <cmath>
+
+using namespace std;
+
+namespace PLMD{
+namespace multicolvar{
+
+//+PLUMEDOC MCOLVAR XYTORSIONS
+/*
+Calculate the torsional angle around the x axis from the positive y direction.
+
+\par Examples
+
+The following input tells plumed to calculate the angle around the x direction between the positive y-axis and the vector connecting atom 3 to atom 5 and
+the angle around the x direction between the positive y axis and the vector connecting atom 1 to atom 2. The minimum of these two quantities is then output
+\verbatim
+XYTORSIONS ATOMS1=3,5 ATOMS2=1,2 MIN={BETA=0.1} LABEL=d1
+PRINT ARG=d1.min
+\endverbatim
+(See also \ref PRINT).
+*/
+//+ENDPLUMEDOC
+
+//+PLUMEDOC MCOLVAR XZTORSIONS
+/*
+Calculate the torsional angle around the x axis from the positive z direction.
+
+\par Examples
+
+The following input tells plumed to calculate the angle around the x direction between the positive z-axis and the vector connecting atom 3 to atom 5 and
+the angle around the x direction between the positive z direction and the vector connecting atom 1 to atom 2. The minimum of these two quantities is then output
+\verbatim
+XZTORSIONS ATOMS1=3,5 ATOMS2=1,2 MIN={BETA=0.1} LABEL=d1
+PRINT ARG=d1.min
+\endverbatim
+(See also \ref PRINT).
+*/
+//+ENDPLUMEDOC
+
+//+PLUMEDOC MCOLVAR YXTORSIONS
+/*
+Calculate the torsional angle around the y axis from the positive x direction.
+
+\par Examples
+
+The following input tells plumed to calculate the angle around the y direction between the positive x-direction and the vector connecting atom 3 to atom 5 and
+the angle around the y direction between the positive x axis and the vector connecting atom 1 to atom 2. The minimum of these two quantities is then output
+\verbatim
+YXTORSIONS ATOMS1=3,5 ATOMS2=1,2 MIN={BETA=0.1} LABEL=d1
+PRINT ARG=d1.min
+\endverbatim
+(See also \ref PRINT).
+*/
+//+ENDPLUMEDOC
+
+//+PLUMEDOC MCOLVAR YZTORSIONS
+/*
+Calculate the torsional angle around the y axis from the positive z direction.
+
+\par Examples
+
+The following input tells plumed to calculate the angle around the y direction between the positive z-direction and the vector connecting atom 3 to atom 5 and
+the angle around the y direction between the positive z direction and the vector connecting atom 1 to atom 2. The minimum of these two quantities is then output
+\verbatim
+YZTORSIONS ATOMS1=3,5 ATOMS2=1,2 MIN={BETA=0.1} LABEL=d1
+PRINT ARG=d1.min
+\endverbatim
+(See also \ref PRINT).
+*/
+//+ENDPLUMEDOC
+
+//+PLUMEDOC MCOLVAR ZXTORSIONS
+/*
+Calculate the torsional angle around the z axis from the positive x direction.
+
+\par Examples
+
+The following input tells plumed to calculate the angle around the z direction between the positive x-direction and the vector connecting atom 3 to atom 5 and
+the angle around the z direction between the positive x-direction and the vector connecting atom 1 to atom 2. The minimum of these two quantities is then output
+\verbatim
+ZXTORSIONS ATOMS1=3,5 ATOMS2=1,2 MIN={BETA=0.1} LABEL=d1
+PRINT ARG=d1.min
+\endverbatim
+(See also \ref PRINT).
+*/
+//+ENDPLUMEDOC
+
+//+PLUMEDOC MCOLVAR ZYTORSIONS
+/*
+Calculate the torsional angle around the z axis from the positive y direction.
+
+\par Examples
+
+The following input tells plumed to calculate the angle around the z direction between the positive y-axis and the vector connecting atom 3 to atom 5 and
+the angle around the z direction between the positive y axis and the vector connecting atom 1 to atom 2. The minimum of these two quantities is then output
+\verbatim
+ZYTORSIONS ATOMS1=3,5 ATOMS2=1,2 MIN={BETA=0.1} LABEL=d1
+PRINT ARG=d1.min
+\endverbatim
+(See also \ref PRINT).
+*/
+//+ENDPLUMEDOC
+
+
+
+
+class XYTorsion : public MultiColvar {
+private:
+ bool use_sf;
+ unsigned myc1, myc2;
+ SwitchingFunction sf1;
+public:
+ static void registerKeywords( Keywords& keys );
+ explicit XYTorsion(const ActionOptions&);
+// active methods:
+ virtual double compute( const unsigned& tindex, AtomValuePack& myatoms ) const ;
+ double calculateWeight( const unsigned& taskCode, const double& weight, AtomValuePack& ) const ;
+/// Returns the number of coordinates of the field
+ bool isPeriodic(){ return false; }
+};
+
+PLUMED_REGISTER_ACTION(XYTorsion,"XYTORSIONS")
+PLUMED_REGISTER_ACTION(XYTorsion,"XZTORSIONS")
+PLUMED_REGISTER_ACTION(XYTorsion,"YXTORSIONS")
+PLUMED_REGISTER_ACTION(XYTorsion,"YZTORSIONS")
+PLUMED_REGISTER_ACTION(XYTorsion,"ZXTORSIONS")
+PLUMED_REGISTER_ACTION(XYTorsion,"ZYTORSIONS")
+
+void XYTorsion::registerKeywords( Keywords& keys ){
+ MultiColvar::registerKeywords( keys );
+ keys.use("ATOMS"); keys.use("MAX"); keys.use("ALT_MIN");
+ keys.use("MEAN"); keys.use("MIN");
+ keys.use("LOWEST"); keys.use("HIGHEST");
+ keys.use("BETWEEN"); keys.use("HISTOGRAM"); keys.use("MOMENTS");
+ keys.add("atoms-1","GROUP","Calculate the distance between each distinct pair of atoms in the group");
+ keys.add("atoms-2","GROUPA","Calculate the distances between all the atoms in GROUPA and all "
+ "the atoms in GROUPB. This must be used in conjuction with GROUPB.");
+ keys.add("atoms-2","GROUPB","Calculate the distances between all the atoms in GROUPA and all the atoms "
+ "in GROUPB. This must be used in conjuction with GROUPA.");
+ keys.add("optional","SWITCH","A switching function that ensures that only angles are only computed when atoms are within "
+ "are within a certain fixed cutoff. The following provides information on the \\ref switchingfunction that are available.");
+}
+
+XYTorsion::XYTorsion(const ActionOptions&ao):
+PLUMED_MULTICOLVAR_INIT(ao),
+use_sf(false)
+{
+ if( getName().find("XY")!=std::string::npos){ myc1=0; myc2=1; }
+ else if( getName().find("XZ")!=std::string::npos){ myc1=0; myc2=2; }
+ else if( getName().find("YX")!=std::string::npos){ myc1=1; myc2=0; }
+ else if( getName().find("YZ")!=std::string::npos){ myc1=1; myc2=2; }
+ else if( getName().find("ZX")!=std::string::npos){ myc1=2; myc2=0; }
+ else if( getName().find("ZY")!=std::string::npos){ myc1=2; myc2=1; }
+ else plumed_error();
+
+ // Read in switching function
+ std::string sfinput, errors; parse("SWITCH",sfinput);
+ if( sfinput.length()>0 ){
+ use_sf=true; weightHasDerivatives=true;
+ sf1.set(sfinput,errors);
+ if( errors.length()!=0 ) error("problem reading SWITCH keyword : " + errors );
+ log.printf(" only calculating angles for atoms separated by less than %s\n", sf1.description().c_str() );
+ setLinkCellCutoff( sf1.get_dmax() );
+ }
+
+ // Read in the atoms
+ std::vector<AtomNumber> all_atoms;
+ readTwoGroups( "GROUP", "GROUPA", "GROUPB", all_atoms );
+ int natoms=2; readAtoms( natoms, all_atoms );
+ // And check everything has been read in correctly
+ checkRead();
+}
+
+double XYTorsion::calculateWeight( const unsigned& taskCode, const double& weight, AtomValuePack& myatoms ) const {
+ if(!use_sf) return 1.0;
+
+ Vector distance=getSeparation( myatoms.getPosition(0), myatoms.getPosition(1) );
+ double dw, w = sf1.calculateSqr( distance.modulo2(), dw );
+ addAtomDerivatives( 0, 0, (-dw)*distance, myatoms );
+ addAtomDerivatives( 0, 1, (+dw)*distance, myatoms );
+ myatoms.addBoxDerivatives( 0, (-dw)*Tensor(distance,distance) );
+ return w;
+}
+
+double XYTorsion::compute( const unsigned& tindex, AtomValuePack& myatoms ) const {
+ Vector dd0, dd1, dd2, axis, rot, distance;
+ axis.zero(); rot.zero(); rot[myc1]=1; axis[myc2]=1;
+ distance=getSeparation( myatoms.getPosition(0), myatoms.getPosition(1) );
+ PLMD::Torsion t; double torsion=t.compute( distance, rot, axis, dd0, dd1, dd2 );
+
+ addAtomDerivatives( 1, 0, -dd0, myatoms );
+ addAtomDerivatives( 1, 1, dd0, myatoms );
+ myatoms.addBoxDerivatives( 1, -extProduct(distance,dd0) );
+ return torsion;
+}
+
+}
+}
+