[Pw_forum] Broken degeneracy using B3LYP

[Jeremy McMinis]

Hello,

I am using the B3LYP functional and notice that degeneracies are being
broken. Do I need to use a specific diagonalization method or is there
something else I need to be doing to avoid this problem? I am running
with sym and inv .false. because I want the k-points to generate
orbitals. This doesn't effect the LDA calculation.

======================================
For instance, running Silicon Carbide in a cubic cell and 2x2x2
K-point tiling I get the lowest occupied orbitals from LDA as,
energy=-0.27368 k=( 0.0000,  0.0000,  0.0000)
energy=-0.13866 k=( 0.3813,  0.3813,  0.3813)
energy=-0.13866 k=(-0.3813,  0.3813, -0.3813)
energy=-0.13866 k=(-0.3813, -0.3813,  0.3813)
energy=-0.13866 k=(-0.3813,  0.3813,  0.3813)
energy=-0.08071 k=( 0.0000,  0.0000,  0.7626)
energy=-0.08071 k=( 0.0000,  0.7626,  0.0000)
energy=-0.08071 k=(-0.7626,  0.0000,  0.0000)
energy=-0.00732 k=(-0.3813,  0.3813,  0.3813)
energy=-0.00732 k=(-0.3813, -0.3813,  0.3813)
energy=-0.00732 k=(-0.3813,  0.3813, -0.3813)
energy=-0.00732 k=( 0.3813,  0.3813,  0.3813)
energy= 0.01591 k=(-0.7626,  0.0000,  0.0000)
energy= 0.01591 k=( 0.0000,  0.0000,  0.7626)
energy= 0.01591 k=( 0.0000,  0.7626,  0.0000)
energy= 0.19069 k=( 0.0000,  0.7626,  0.0000)
energy= 0.19069 k=( 0.0000,  0.0000,  0.7626)
energy= 0.19069 k=(-0.7626,  0.0000,  0.0000)
energy= 0.19069 k=(-0.7626,  0.0000,  0.0000)
energy= 0.19069 k=( 0.0000,  0.0000,  0.7626)
energy= 0.19069 k=( 0.0000,  0.7626,  0.0000)
energy= 0.26820 k=( 0.3813,  0.3813,  0.3813)
energy= 0.26820 k=(-0.3813, -0.3813,  0.3813)
energy= 0.26820 k=(-0.3813,  0.3813, -0.3813)
energy= 0.26820 k=(-0.3813,  0.3813,  0.3813)
energy= 0.26820 k=( 0.3813,  0.3813,  0.3813)
energy= 0.26820 k=(-0.3813,  0.3813, -0.3813)
energy= 0.26820 k=(-0.3813,  0.3813,  0.3813)
energy= 0.26820 k=(-0.3813, -0.3813,  0.3813)
energy= 0.30662 k=( 0.0000,  0.0000,  0.0000)
energy= 0.30662 k=( 0.0000,  0.0000,  0.0000)
energy= 0.30662 k=( 0.0000,  0.0000,  0.0000)

and from B3LYP as :
energy=-0.21040 k=( 0.0000,  0.0000,  0.0000)
energy=-0.07163 k=(-0.3813,  0.3813, -0.3813)
energy=-0.07163 k=( 0.3813,  0.3813,  0.3813)
energy=-0.07163 k=(-0.3813, -0.3813,  0.3813)
energy=-0.07162 k=(-0.3813,  0.3813,  0.3813)
energy=-0.01393 k=(-0.7626,  0.0000,  0.0000)
energy=-0.01393 k=( 0.0000,  0.7626,  0.0000)
energy=-0.01393 k=( 0.0000,  0.0000,  0.7626)
energy= 0.03976 k=(-0.3813,  0.3813,  0.3813)
energy= 0.03977 k=(-0.3813, -0.3813,  0.3813)
energy= 0.03977 k=( 0.3813,  0.3813,  0.3813)
energy= 0.03978 k=(-0.3813,  0.3813, -0.3813)
energy= 0.06856 k=( 0.0000,  0.0000,  0.7626)
energy= 0.06856 k=( 0.0000,  0.7626,  0.0000)
energy= 0.06856 k=(-0.7626,  0.0000,  0.0000)
energy= 0.24708 k=(-0.7626,  0.0000,  0.0000)
energy= 0.24708 k=( 0.0000,  0.7626,  0.0000)
energy= 0.24708 k=( 0.0000,  0.0000,  0.7626)
energy= 0.24708 k=( 0.0000,  0.0000,  0.7626)
energy= 0.24708 k=(-0.7626,  0.0000,  0.0000)
energy= 0.24708 k=( 0.0000,  0.7626,  0.0000)
energy= 0.33069 k=(-0.3813, -0.3813,  0.3813)
energy= 0.33069 k=(-0.3813,  0.3813, -0.3813)
energy= 0.33070 k=( 0.3813,  0.3813,  0.3813)
energy= 0.33070 k=(-0.3813,  0.3813,  0.3813)
energy= 0.33070 k=(-0.3813,  0.3813, -0.3813)
energy= 0.33071 k=(-0.3813,  0.3813,  0.3813)
energy= 0.33071 k=( 0.3813,  0.3813,  0.3813)
energy= 0.33071 k=(-0.3813, -0.3813,  0.3813)
energy= 0.37074 k=( 0.0000,  0.0000,  0.0000)
energy= 0.37075 k=( 0.0000,  0.0000,  0.0000)
energy= 0.37076 k=( 0.0000,  0.0000,  0.0000)

======================================
 &control
   prefix= "dft.sic.222",
   pseudo_dir = '../',
   outdir='.',
   wf_collect=.true.,
/
 &system
   ibrav=  2, celldm(1) =8.2392, nat=  2, ntyp= 2,
   ecutwfc = 200, nelec=8, nbnd=6,
   input_dft= "B3LYP",
   nosym=.true.,
   noinv=.true.,
 /
 &electrons
 /
ATOMIC_SPECIES
 C  14.0     C.DF.upf
 Si  28.086  Si.DF.upf
ATOMIC_POSITIONS
 C 0.00 0.00 0.00
 Si 0.25 0.25 0.25
K_POINTS automatic
2 2 2 0 0 0