diff --git a/src/CLASS2/improper_class2.h b/src/CLASS2/improper_class2.h
index fc845cbf51..0017c04892 100644
--- a/src/CLASS2/improper_class2.h
+++ b/src/CLASS2/improper_class2.h
@@ -27,12 +27,12 @@ namespace LAMMPS_NS {
 class ImproperClass2 : public Improper {
  public:
   ImproperClass2(class LAMMPS *);
-  virtual ~ImproperClass2();
-  virtual void compute(int, int);
-  virtual void coeff(int, char **);
-  void write_restart(FILE *);
-  virtual void read_restart(FILE *);
-  void write_data(FILE *);
+  ~ImproperClass2() override;
+  void compute(int, int) override;
+  void coeff(int, char **) override;
+  void write_restart(FILE *) override;
+  void read_restart(FILE *) override;
+  void write_data(FILE *) override;
 
  protected:
   double *k0, *chi0;
diff --git a/src/EXTRA-MOLECULE/improper_cossq.h b/src/EXTRA-MOLECULE/improper_cossq.h
index fd22e438ce..854aa3ed05 100644
--- a/src/EXTRA-MOLECULE/improper_cossq.h
+++ b/src/EXTRA-MOLECULE/improper_cossq.h
@@ -27,12 +27,12 @@ namespace LAMMPS_NS {
 class ImproperCossq : public Improper {
  public:
   ImproperCossq(class LAMMPS *);
-  virtual ~ImproperCossq();
-  virtual void compute(int, int);
-  void coeff(int, char **);
-  void write_restart(FILE *);
-  void read_restart(FILE *);
-  void write_data(FILE *);
+  ~ImproperCossq() override;
+  void compute(int, int) override;
+  void coeff(int, char **) override;
+  void write_restart(FILE *) override;
+  void read_restart(FILE *) override;
+  void write_data(FILE *) override;
 
  protected:
   double *k, *chi;
diff --git a/src/EXTRA-MOLECULE/improper_distance.h b/src/EXTRA-MOLECULE/improper_distance.h
index fbf8060c9f..d814405906 100644
--- a/src/EXTRA-MOLECULE/improper_distance.h
+++ b/src/EXTRA-MOLECULE/improper_distance.h
@@ -27,12 +27,12 @@ namespace LAMMPS_NS {
 class ImproperDistance : public Improper {
  public:
   ImproperDistance(class LAMMPS *);
-  ~ImproperDistance();
-  void compute(int, int);
-  void coeff(int, char **);
-  void write_restart(FILE *);
-  void read_restart(FILE *);
-  void write_data(FILE *);
+  ~ImproperDistance() override;
+  void compute(int, int) override;
+  void coeff(int, char **) override;
+  void write_restart(FILE *) override;
+  void read_restart(FILE *) override;
+  void write_data(FILE *) override;
 
  private:
   double *k, *chi;
diff --git a/src/EXTRA-MOLECULE/improper_fourier.h b/src/EXTRA-MOLECULE/improper_fourier.h
index 25d03e623b..f420c534a2 100644
--- a/src/EXTRA-MOLECULE/improper_fourier.h
+++ b/src/EXTRA-MOLECULE/improper_fourier.h
@@ -27,12 +27,12 @@ namespace LAMMPS_NS {
 class ImproperFourier : public Improper {
  public:
   ImproperFourier(class LAMMPS *);
-  ~ImproperFourier();
-  void compute(int, int);
-  void coeff(int, char **);
-  void write_restart(FILE *);
-  void read_restart(FILE *);
-  void write_data(FILE *);
+  ~ImproperFourier() override;
+  void compute(int, int) override;
+  void coeff(int, char **) override;
+  void write_restart(FILE *) override;
+  void read_restart(FILE *) override;
+  void write_data(FILE *) override;
 
  protected:
   double *k, *C0, *C1, *C2;
diff --git a/src/EXTRA-MOLECULE/improper_ring.h b/src/EXTRA-MOLECULE/improper_ring.h
index f428a7bfd6..3afb5a8d98 100644
--- a/src/EXTRA-MOLECULE/improper_ring.h
+++ b/src/EXTRA-MOLECULE/improper_ring.h
@@ -27,12 +27,12 @@ namespace LAMMPS_NS {
 class ImproperRing : public Improper {
  public:
   ImproperRing(class LAMMPS *);
-  virtual ~ImproperRing();
-  virtual void compute(int, int);
-  void coeff(int, char **);
-  void write_restart(FILE *);
-  void read_restart(FILE *);
-  void write_data(FILE *);
+  ~ImproperRing() override;
+  void compute(int, int) override;
+  void coeff(int, char **) override;
+  void write_restart(FILE *) override;
+  void read_restart(FILE *) override;
+  void write_data(FILE *) override;
 
  protected:
   double *k, *chi;
diff --git a/src/INTEL/improper_cvff_intel.h b/src/INTEL/improper_cvff_intel.h
index 6ea95d0ff4..f09cc06a0d 100644
--- a/src/INTEL/improper_cvff_intel.h
+++ b/src/INTEL/improper_cvff_intel.h
@@ -33,9 +33,9 @@ namespace LAMMPS_NS {
 class ImproperCvffIntel : public ImproperCvff {
  public:
   ImproperCvffIntel(class LAMMPS *);
-  virtual ~ImproperCvffIntel();
-  virtual void compute(int, int);
-  virtual void init_style();
+  ~ImproperCvffIntel() override;
+  void compute(int, int) override;
+  void init_style() override;
 
  protected:
   FixIntel *fix;
diff --git a/src/INTEL/improper_harmonic_intel.h b/src/INTEL/improper_harmonic_intel.h
index 3b9c5d2ec9..b8218614e1 100644
--- a/src/INTEL/improper_harmonic_intel.h
+++ b/src/INTEL/improper_harmonic_intel.h
@@ -33,9 +33,9 @@ namespace LAMMPS_NS {
 class ImproperHarmonicIntel : public ImproperHarmonic {
  public:
   ImproperHarmonicIntel(class LAMMPS *);
-  virtual ~ImproperHarmonicIntel();
-  virtual void compute(int, int);
-  virtual void init_style();
+  ~ImproperHarmonicIntel() override;
+  void compute(int, int) override;
+  void init_style() override;
 
  protected:
   FixIntel *fix;
diff --git a/src/KOKKOS/improper_class2_kokkos.h b/src/KOKKOS/improper_class2_kokkos.h
index 9656526e49..179a7b61a9 100644
--- a/src/KOKKOS/improper_class2_kokkos.h
+++ b/src/KOKKOS/improper_class2_kokkos.h
@@ -42,10 +42,10 @@ class ImproperClass2Kokkos : public ImproperClass2 {
   typedef ArrayTypes<DeviceType> AT;
 
   ImproperClass2Kokkos(class LAMMPS *);
-  virtual ~ImproperClass2Kokkos();
-  void compute(int, int);
-  void coeff(int, char **);
-  void read_restart(FILE *);
+  ~ImproperClass2Kokkos() override;
+  void compute(int, int) override;
+  void coeff(int, char **) override;
+  void read_restart(FILE *) override;
 
   template<int NEWTON_BOND, int EVFLAG>
   KOKKOS_INLINE_FUNCTION
diff --git a/src/KOKKOS/improper_harmonic_kokkos.h b/src/KOKKOS/improper_harmonic_kokkos.h
index ad683f314d..02cbb9d15a 100644
--- a/src/KOKKOS/improper_harmonic_kokkos.h
+++ b/src/KOKKOS/improper_harmonic_kokkos.h
@@ -39,10 +39,10 @@ class ImproperHarmonicKokkos : public ImproperHarmonic {
   typedef ArrayTypes<DeviceType> AT;
 
   ImproperHarmonicKokkos(class LAMMPS *);
-  virtual ~ImproperHarmonicKokkos();
-  void compute(int, int);
-  void coeff(int, char **);
-  void read_restart(FILE *);
+  ~ImproperHarmonicKokkos() override;
+  void compute(int, int) override;
+  void coeff(int, char **) override;
+  void read_restart(FILE *) override;
 
   template<int NEWTON_BOND, int EVFLAG>
   KOKKOS_INLINE_FUNCTION
@@ -87,7 +87,7 @@ class ImproperHarmonicKokkos : public ImproperHarmonic {
   typename Kokkos::DualView<F_FLOAT*,DeviceType>::t_dev d_k;
   typename Kokkos::DualView<F_FLOAT*,DeviceType>::t_dev d_chi;
 
-  void allocate();
+  void allocate() override;
 };
 
 }
diff --git a/src/MOFFF/improper_inversion_harmonic.h b/src/MOFFF/improper_inversion_harmonic.h
index 5ab8e78a3c..e3bf1a0bc5 100644
--- a/src/MOFFF/improper_inversion_harmonic.h
+++ b/src/MOFFF/improper_inversion_harmonic.h
@@ -27,12 +27,12 @@ namespace LAMMPS_NS {
 class ImproperInversionHarmonic : public Improper {
  public:
   ImproperInversionHarmonic(class LAMMPS *);
-  virtual ~ImproperInversionHarmonic();
-  virtual void compute(int, int);
-  void coeff(int, char **);
-  void write_restart(FILE *);
-  void read_restart(FILE *);
-  void write_data(FILE *);
+  ~ImproperInversionHarmonic() override;
+  void compute(int, int) override;
+  void coeff(int, char **) override;
+  void write_restart(FILE *) override;
+  void read_restart(FILE *) override;
+  void write_data(FILE *) override;
 
  protected:
   double *kw, *w0;
diff --git a/src/MOLECULE/improper_cvff.h b/src/MOLECULE/improper_cvff.h
index 821d29e607..1e724bc84b 100644
--- a/src/MOLECULE/improper_cvff.h
+++ b/src/MOLECULE/improper_cvff.h
@@ -27,12 +27,12 @@ namespace LAMMPS_NS {
 class ImproperCvff : public Improper {
  public:
   ImproperCvff(class LAMMPS *);
-  virtual ~ImproperCvff();
-  virtual void compute(int, int);
-  void coeff(int, char **);
-  void write_restart(FILE *);
-  void read_restart(FILE *);
-  void write_data(FILE *);
+  ~ImproperCvff() override;
+  void compute(int, int) override;
+  void coeff(int, char **) override;
+  void write_restart(FILE *) override;
+  void read_restart(FILE *) override;
+  void write_data(FILE *) override;
 
  protected:
   double *k;
diff --git a/src/MOLECULE/improper_harmonic.h b/src/MOLECULE/improper_harmonic.h
index d81a81f951..64966b477c 100644
--- a/src/MOLECULE/improper_harmonic.h
+++ b/src/MOLECULE/improper_harmonic.h
@@ -27,12 +27,12 @@ namespace LAMMPS_NS {
 class ImproperHarmonic : public Improper {
  public:
   ImproperHarmonic(class LAMMPS *);
-  virtual ~ImproperHarmonic();
-  virtual void compute(int, int);
-  virtual void coeff(int, char **);
-  void write_restart(FILE *);
-  virtual void read_restart(FILE *);
-  void write_data(FILE *);
+  ~ImproperHarmonic() override;
+  void compute(int, int) override;
+  void coeff(int, char **) override;
+  void write_restart(FILE *) override;
+  void read_restart(FILE *) override;
+  void write_data(FILE *) override;
 
  protected:
   double *k, *chi;
diff --git a/src/MOLECULE/improper_umbrella.h b/src/MOLECULE/improper_umbrella.h
index 836527ee3c..fb671646e7 100644
--- a/src/MOLECULE/improper_umbrella.h
+++ b/src/MOLECULE/improper_umbrella.h
@@ -27,12 +27,12 @@ namespace LAMMPS_NS {
 class ImproperUmbrella : public Improper {
  public:
   ImproperUmbrella(class LAMMPS *);
-  virtual ~ImproperUmbrella();
-  virtual void compute(int, int);
-  void coeff(int, char **);
-  void write_restart(FILE *);
-  void read_restart(FILE *);
-  void write_data(FILE *);
+  ~ImproperUmbrella() override;
+  void compute(int, int) override;
+  void coeff(int, char **) override;
+  void write_restart(FILE *) override;
+  void read_restart(FILE *) override;
+  void write_data(FILE *) override;
 
  protected:
   double *kw, *w0, *C;
diff --git a/src/OPENMP/improper_class2_omp.h b/src/OPENMP/improper_class2_omp.h
index 4930e5795d..efb1f67c4c 100644
--- a/src/OPENMP/improper_class2_omp.h
+++ b/src/OPENMP/improper_class2_omp.h
@@ -33,7 +33,7 @@ class ImproperClass2OMP : public ImproperClass2, public ThrOMP {
 
  public:
   ImproperClass2OMP(class LAMMPS *lmp);
-  virtual void compute(int, int);
+  void compute(int, int) override;
 
  private:
   template <int EVFLAG, int EFLAG, int NEWTON_BOND>
diff --git a/src/OPENMP/improper_cossq_omp.h b/src/OPENMP/improper_cossq_omp.h
index 98069222b3..515ee0d076 100644
--- a/src/OPENMP/improper_cossq_omp.h
+++ b/src/OPENMP/improper_cossq_omp.h
@@ -33,7 +33,7 @@ class ImproperCossqOMP : public ImproperCossq, public ThrOMP {
 
  public:
   ImproperCossqOMP(class LAMMPS *lmp);
-  virtual void compute(int, int);
+  void compute(int, int) override;
 
  private:
   template <int EVFLAG, int EFLAG, int NEWTON_BOND>
diff --git a/src/OPENMP/improper_cvff_omp.h b/src/OPENMP/improper_cvff_omp.h
index b994ec0547..04faba38ac 100644
--- a/src/OPENMP/improper_cvff_omp.h
+++ b/src/OPENMP/improper_cvff_omp.h
@@ -33,7 +33,7 @@ class ImproperCvffOMP : public ImproperCvff, public ThrOMP {
 
  public:
   ImproperCvffOMP(class LAMMPS *lmp);
-  virtual void compute(int, int);
+  void compute(int, int) override;
 
  private:
   template <int EVFLAG, int EFLAG, int NEWTON_BOND>
diff --git a/src/OPENMP/improper_fourier_omp.h b/src/OPENMP/improper_fourier_omp.h
index 734b17e101..e9b63b68dc 100644
--- a/src/OPENMP/improper_fourier_omp.h
+++ b/src/OPENMP/improper_fourier_omp.h
@@ -33,7 +33,7 @@ class ImproperFourierOMP : public ImproperFourier, public ThrOMP {
 
  public:
   ImproperFourierOMP(class LAMMPS *lmp);
-  virtual void compute(int, int);
+  void compute(int, int) override;
 
  private:
   template <int EVFLAG, int EFLAG, int NEWTON_BOND>
diff --git a/src/OPENMP/improper_harmonic_omp.h b/src/OPENMP/improper_harmonic_omp.h
index 78eb32e505..4caf47d56e 100644
--- a/src/OPENMP/improper_harmonic_omp.h
+++ b/src/OPENMP/improper_harmonic_omp.h
@@ -33,7 +33,7 @@ class ImproperHarmonicOMP : public ImproperHarmonic, public ThrOMP {
 
  public:
   ImproperHarmonicOMP(class LAMMPS *lmp);
-  virtual void compute(int, int);
+  void compute(int, int) override;
 
  private:
   template <int EVFLAG, int EFLAG, int NEWTON_BOND>
diff --git a/src/OPENMP/improper_ring_omp.h b/src/OPENMP/improper_ring_omp.h
index 9199830be7..7adce7014c 100644
--- a/src/OPENMP/improper_ring_omp.h
+++ b/src/OPENMP/improper_ring_omp.h
@@ -33,7 +33,7 @@ class ImproperRingOMP : public ImproperRing, public ThrOMP {
 
  public:
   ImproperRingOMP(class LAMMPS *lmp);
-  virtual void compute(int, int);
+  void compute(int, int) override;
 
  private:
   template <int EVFLAG, int EFLAG, int NEWTON_BOND>
diff --git a/src/OPENMP/improper_umbrella_omp.h b/src/OPENMP/improper_umbrella_omp.h
index 17dd81ca80..81f1a05787 100644
--- a/src/OPENMP/improper_umbrella_omp.h
+++ b/src/OPENMP/improper_umbrella_omp.h
@@ -33,7 +33,7 @@ class ImproperUmbrellaOMP : public ImproperUmbrella, public ThrOMP {
 
  public:
   ImproperUmbrellaOMP(class LAMMPS *lmp);
-  virtual void compute(int, int);
+  void compute(int, int) override;
 
  private:
   template <int EVFLAG, int EFLAG, int NEWTON_BOND>
diff --git a/src/YAFF/improper_distharm.h b/src/YAFF/improper_distharm.h
index e30c63981c..ebc4c701d5 100644
--- a/src/YAFF/improper_distharm.h
+++ b/src/YAFF/improper_distharm.h
@@ -27,11 +27,11 @@ namespace LAMMPS_NS {
 class ImproperDistHarm : public Improper {
  public:
   ImproperDistHarm(class LAMMPS *);
-  ~ImproperDistHarm();
-  void compute(int, int);
-  void coeff(int, char **);
-  void write_restart(FILE *);
-  void read_restart(FILE *);
+  ~ImproperDistHarm() override;
+  void compute(int, int) override;
+  void coeff(int, char **) override;
+  void write_restart(FILE *) override;
+  void read_restart(FILE *) override;
 
  private:
   double *k, *chi;
diff --git a/src/YAFF/improper_sqdistharm.h b/src/YAFF/improper_sqdistharm.h
index 57727929de..e7a1e62661 100644
--- a/src/YAFF/improper_sqdistharm.h
+++ b/src/YAFF/improper_sqdistharm.h
@@ -27,11 +27,11 @@ namespace LAMMPS_NS {
 class ImproperSQDistHarm : public Improper {
  public:
   ImproperSQDistHarm(class LAMMPS *);
-  ~ImproperSQDistHarm();
-  void compute(int, int);
-  void coeff(int, char **);
-  void write_restart(FILE *);
-  void read_restart(FILE *);
+  ~ImproperSQDistHarm() override;
+  void compute(int, int) override;
+  void coeff(int, char **) override;
+  void write_restart(FILE *) override;
+  void read_restart(FILE *) override;
 
  private:
   double *k, *chi;
diff --git a/src/improper_deprecated.h b/src/improper_deprecated.h
index ea080ba3cb..d2f0be0dc3 100644
--- a/src/improper_deprecated.h
+++ b/src/improper_deprecated.h
@@ -27,13 +27,12 @@ namespace LAMMPS_NS {
 class ImproperDeprecated : public Improper {
  public:
   ImproperDeprecated(class LAMMPS *lmp) : Improper(lmp) {}
-  virtual ~ImproperDeprecated() {}
 
-  virtual void compute(int, int) {}
-  virtual void settings(int, char **);
-  virtual void coeff(int, char **) {}
-  virtual void write_restart(FILE *) {}
-  virtual void read_restart(FILE *) {}
+  void compute(int, int) override {}
+  void settings(int, char **) override;
+  void coeff(int, char **) override {}
+  void write_restart(FILE *) override {}
+  void read_restart(FILE *) override {}
 };
 
 }    // namespace LAMMPS_NS
diff --git a/src/improper_hybrid.h b/src/improper_hybrid.h
index e680ec9119..caa9e0b762 100644
--- a/src/improper_hybrid.h
+++ b/src/improper_hybrid.h
@@ -31,14 +31,14 @@ class ImproperHybrid : public Improper {
   char **keywords;      // keyword for each improper style
 
   ImproperHybrid(class LAMMPS *);
-  ~ImproperHybrid();
-  void init_style();
-  void compute(int, int);
-  void settings(int, char **);
-  void coeff(int, char **);
-  void write_restart(FILE *);
-  void read_restart(FILE *);
-  double memory_usage();
+  ~ImproperHybrid() override;
+  void init_style() override;
+  void compute(int, int) override;
+  void settings(int, char **) override;
+  void coeff(int, char **) override;
+  void write_restart(FILE *) override;
+  void read_restart(FILE *) override;
+  double memory_usage() override;
 
  private:
   int *map;    // which style each improper type points to
diff --git a/src/improper_zero.h b/src/improper_zero.h
index 9b1dfa4e73..5acf34c6d4 100644
--- a/src/improper_zero.h
+++ b/src/improper_zero.h
@@ -27,14 +27,14 @@ namespace LAMMPS_NS {
 class ImproperZero : public Improper {
  public:
   ImproperZero(class LAMMPS *);
-  virtual ~ImproperZero();
-  virtual void compute(int, int);
-  virtual void coeff(int, char **);
-  virtual void settings(int, char **);
+  ~ImproperZero() override;
+  void compute(int, int) override;
+  void coeff(int, char **) override;
+  void settings(int, char **) override;
 
-  void write_restart(FILE *);
-  void read_restart(FILE *);
-  void write_data(FILE *);
+  void write_restart(FILE *) override;
+  void read_restart(FILE *) override;
+  void write_data(FILE *) override;
 
  protected:
   int coeffflag;