add an example to test the old DFT+U method with only scf energy, not force and stress

Author: abacus_fixer

tests/02_NAO_Gamma/scf_u_spin2_old/INPUT

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+INPUT_PARAMETERS 
+suffix            autotest
+nbands            28
+
+calculation       scf
+ecutwfc           6
+scf_thr           1.0e-7
+scf_nmax          30
+out_chg           0
+
+smearing_method   gaussian
+smearing_sigma    0.07
+
+cal_force         0
+cal_stress        0
+
+#force_thr_ev    0.01
+#relax_method    cg
+#relax_bfgs_init    0.5
+
+mixing_type       broyden
+mixing_beta       0.2
+mixing_gg0        1.0
+
+ks_solver         scalapack_gvx
+basis_type        lcao
+gamma_only        1
+symmetry          0
+nspin             2
+
+#Parameter DFT+U
+dft_plus_u        2 # 1: new 2: old
+orbital_corr      2 2
+hubbard_u         5.0 5.0
+onsite_radius     5.0
+pseudo_dir        ../../PP_ORB
+orbital_dir       ../../PP_ORB

tests/02_NAO_Gamma/scf_u_spin2_old/README

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+DFTU + NSPIN2 but use old DFTU method, Fe2O2, gamma-only case

tests/02_NAO_Gamma/scf_u_spin2_old/STRU

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+ATOMIC_SPECIES
+Fe 1.000 Fe_ONCV_PBE-1.0.upf
+O  1.000 O_ONCV_PBE-1.0.upf
+
+NUMERICAL_ORBITAL
+Fe_gga_6au_100Ry_2s1p1d.orb
+O_gga_7au_60Ry_2s2p1d.orb
+
+LATTICE_CONSTANT
+8.190
+
+LATTICE_VECTORS
+ 1.00    0.50     0.50
+ 0.50    1.00     0.50
+ 0.50    0.50     1.00
+ATOMIC_POSITIONS
+Direct
+
+Fe
+0.0
+2
+0.00            0.00            0.00         mag  1.0
+0.50            0.50            0.50         mag  -1.0
+
+O
+0.0
+2
+0.25            0.25            0.25            1        1       1
+0.75            0.75            0.75            1        1       1

tests/02_NAO_Gamma/scf_u_spin2_old/result.ref

@@ -0,0 +1,3 @@
+etotref -6304.2287463338798261
+etotperatomref -1576.0571865835
+totaltimeref 1.17