enable lj96 for fix adapt

doc/src/fix_adapt.rst

@@ -178,6 +178,8 @@ formulas for the meaning of these parameters:
 +------------------------------------------------------------------------------+--------------------------------------------------+-------------+
 | :doc:`lennard/mdf <pair_mdf>`                                                | A,B                                              | type pairs  |
 +------------------------------------------------------------------------------+--------------------------------------------------+-------------+
+| :doc:`lj96/cut <pair_lj96>`                                                  | epsilon,sigma                                    | type pairs  |
++------------------------------------------------------------------------------+--------------------------------------------------+-------------+
 | :doc:`lj/class2 <pair_class2>`                                               | epsilon,sigma                                    | type pairs  |
 +------------------------------------------------------------------------------+--------------------------------------------------+-------------+
 | :doc:`lj/class2/coul/cut, lj/class2/coul/long <pair_class2>`                 | epsilon,sigma,coulombic_cutoff                   | type pairs  |

src/EXTRA-PAIR/pair_lj96_cut.cpp

@@ -707,3 +707,12 @@ void PairLJ96Cut::born_matrix(int /*i*/, int /*j*/, int itype, int jtype, double
   du2pair = factor_lj * du2;
 }
 
+/* ---------------------------------------------------------------------- */
+
+void *PairLJ96Cut::extract(const char *str, int &dim)
+{
+  dim = 2;
+  if (strcmp(str, "epsilon") == 0) return (void *) epsilon;
+  if (strcmp(str, "sigma") == 0) return (void *) sigma;
+  return nullptr;
+}

src/EXTRA-PAIR/pair_lj96_cut.h

@@ -42,6 +42,7 @@ class PairLJ96Cut : public Pair {
   void write_data_all(FILE *) override;
   double single(int, int, int, int, double, double, double, double &) override;
   void born_matrix(int, int, int, int, double, double, double, double &, double &) override;
+  void *extract(const char *, int &) override;
 
   void compute_inner() override;
   void compute_middle() override;

unittest/force-styles/tests/mol-pair-lj96_cut.yaml

@@ -18,7 +18,9 @@ pair_coeff: ! |
   3 3 0.03375   3.2
   4 4 0.0253125 3.1
   5 5 0.0253125 3.1
-extract: ! ""
+extract: ! |
+  epsilon 2
+  sigma 2
 natoms: 29
 init_vdwl: 112.14679117633445
 init_coul: 0