GW: Minor changes for input handling

src/auto_basis.F

@@ -91,6 +91,15 @@ CONTAINS
          CALL get_qs_kind(qs_kind, basis_set=orb_basis_set, basis_type=basis_type)
       END IF
       IF (ASSOCIATED(orb_basis_set)) THEN
+         ! BASIS_SET ORB NONE associates the pointer orb_basis_set, but does not contain
+         ! any actual basis functions. Therefore, we catch it here to avoid spurious autogenerated
+         ! RI_AUX basis sets.
+         IF (SUM(orb_basis_set%nsgf_set) == 0) THEN
+            CALL cp_abort(__LOCATION__, &
+                          "Cannot autocreate RI_AUX basis set for at least one of the given "// &
+                          "primary basis sets due to missing exponents. If you have invoked BASIS_SET NONE, "// &
+                          "you should state BASIS_SET RI_AUX NONE explicitly in the input.")
+         END IF
          CALL get_basis_keyfigures(orb_basis_set, lmax, zmin, zmax, zeff)
          !Note: RI basis coud require lmax up to 2*orb_lmax. This ensures that all orbital pointers
          !      are properly initialized before building the basis

src/gw_utils.F

@@ -1285,6 +1285,20 @@ CONTAINS
          bs_env%Sigma_x_exists = bs_env%Sigma_x_exists .AND. Sigma_x_spin_exists
       END DO
 
+      ! If any restart files are read, check if the SCF converged in 1 step.
+      ! This is important because a re-iterated SCF can lead to spurious GW results
+      IF (ANY(bs_env%read_chi(:)) &
+          .OR. ANY(bs_env%Sigma_c_exists) &
+          .OR. bs_env%all_W_exist &
+          .OR. bs_env%Sigma_x_exists &
+          ) THEN
+
+         IF (qs_env%scf_env%iter_count /= 1) THEN
+            CALL cp_warn(__LOCATION__, "SCF needed more than 1 step, "// &
+                         "which might lead to spurious GW results when using GW restart files. ")
+         END IF
+      END IF
+
       CALL timestop(handle)
 
    END SUBROUTINE check_for_restart_files

src/mp2_eri.F

@@ -741,9 +741,11 @@ CONTAINS
          END IF
 
          basis_set_a => basis_set_list_a(ikind)%gto_basis_set
-         IF (.NOT. ASSOCIATED(basis_set_a)) CYCLE
+         ! When RI_AUX NONE is invoked, the pointers to basis_set_a and basis_set_b are created,
+         ! but not filled. Therefore, we check for the association and the number of entries.
+         IF (.NOT. ASSOCIATED(basis_set_a) .OR. SUM(basis_set_a%nsgf_set) <= 0) CYCLE
          basis_set_b => basis_set_list_b(jkind)%gto_basis_set
-         IF (.NOT. ASSOCIATED(basis_set_b)) CYCLE
+         IF (.NOT. ASSOCIATED(basis_set_b) .OR. SUM(basis_set_b%nsgf_set) <= 0) CYCLE
          atom_a = atom_of_kind(iatom)
          atom_b = atom_of_kind(jatom)