[CPMD-list] Trying to understand screened exchange B3LYP for PBC solids

[driver at mps.ohio-state.edu]

Hello CPMD users,

I am using CPMD-3.11 to do some PBC, many k-point calculations with the
screened B3LYP functional for phases of silica.

What seems bizarre is that a phase calculation will always converge to the
same total energy no matter what options I use with the SCREENED EXCHANGE
keyword. I've tried out ERFC, EXP, and SELF screening while varying the
screening parameter over several orders of magnitude (eg. 10^-4 to 10^2)
for each case. It seems like all the long range Hartree Fock exchange is
always omitted (or always included perhaps).

Is this the behavior I should expect when using SCREENED EXCHANGE, or is
it an indication that I'm not using the code properly (input file is
below)?

The energies I do get seem reasonable - that is, the phase energy
differences I calculate with CPMD-screened-B3LYP agree with all-electron,
unscreened-B3LYP calculations I've done in another code.

Kevin Driver
The Ohio State University, Physics Dept.
driver at mps.ohio-state.edu

------------ Input file -----------------

&INFO
 Stishovite SiO2
 6x6x6 k-point mesh; 6 atoms (primitive cell)
 400 Ryd planewave cutoff energy; B3LYP
&END

&CPMD
  OPTIMIZE WAVEFUNCTION
  CONVERGENCE ORBITALS
   1.0e-6
  PRINT FORCES ON
  MAXSTEP
  1000
&END

&DFT
  FUNCTIONAL B3LYP
  SCREENED EXCHANGE ERFC
      0.1
&END

&SYSTEM
  ANGSTROM
  CELL VECTORS
   4.19311248230   0.00000000000   0.00000000000
   0.00000000000   4.19311248230   0.00000000000
   0.00000000000   0.00000000000   2.68292300360
  CUTOFF
  400.0
  POINT GROUP
  AUTO
  KPOINTS MONKHORST-PACK
  6 6 6
  TESR
  8
&END

&ATOMS
*SI_SG_BLYP  KLEINMAN-BYLANDER
   LMAX=P
   2
   0.000000000000  0.000000000000  0.000000000000
   2.096556241150  2.096556241150  1.341461501800

*O_SG_BLYP KLEINMAN-BYLANDER
   LMAX=P
   4
   1.283524462631  1.283524462631  0.000000000000
  -1.283524462631 -1.283524462631  0.000000000000
  -0.813031778519  0.813031778519  1.341461501800
   0.813031778519 -0.813031778519  1.341461501800
&END