[CPMD-list] concern about the exchange functional

[Eduardo Ariel Menendez P]

Hello CPMD fellows,

In the examples I usually see inputs like this

&DFT
  NEWCODE
  FUNCTIONAL LDA
  GC-CUTOFF
  0.1E-07
&END

and see this in the output:
 EXCHANGE CORRELATION FUNCTIONALS
    LDA EXCHANGE:                                            NONE
    LDA XC THROUGH PADE APPROXIMATION
    S.GOEDECKER, J.HUTTER, M.TETER PRB 54 1703 (1996)

What about the Exchange functional? Aparently it is included
in the Goedecker's Pade approximations.  Am I right?


However, if I input

&DFT
  NEWCODE
  FUNCTIONAL LDA
  LDA CORRELATION PZ
  GC-CUTOFF
  0.1E-07
&END
then I obtain
 EXCHANGE CORRELATION FUNCTIONALS
    LDA EXCHANGE:                                            NONE
    LDA CORRELATION:                              PERDEW & ZUNGER
       [J.P. PERDEW AND A ZUNGER, PRB 23 5048 (1981)]
Here it seems that no Exchange is included

Should I specify the exchange functional, e.g., as follows?
&DFT
  NEWCODE
  FUNCTIONAL LDA
  SLATER
   0.66667
  LDA CORRELATION PZ
  GC-CUTOFF
  0.1E-07
&END
thus obtaining

 EXCHANGE CORRELATION FUNCTIONALS
    LDA EXCHANGE:                        SLATER (ALPHA = 0.66667)
    LDA CORRELATION:                              PERDEW & ZUNGER
       [J.P. PERDEW AND A ZUNGER, PRB 23 5048 (1981)]

Is it correct set to 0.66667 ?

Tkanks in advance
Eduardo

Eduardo A. Menendez Proupin
Department of Physics
Faculty of Science
University of Chile
Las Palmeras 3425
Ñuñoa, Santiago
Chile
Phone: 56+2+678 74 11
http://fisica.ciencias.uchile.cl/~emenendez/