libxc version 7.1.2
S. Lehtola, C. Steigemann, M. J. T. Oliveira, and M. A. L. Marques,  SoftwareX 7, 1–5 (2018)
doi: 10.1016/j.softx.2017.11.002

   func_id: 12                  
      name: lda_c_pw                 
    family: XC_FAMILY_LDA       
      kind: XC_CORRELATION           
   comment: Perdew & Wang

Reference(s):
  *) J. P. Perdew and Y. Wang,  Phys. Rev. B 45, 13244 (1992)
     doi: 10.1103/PhysRevB.45.13244
     bibtex key: Perdew1992_13244

Implementation has support for:
  *) energy
  *) first derivative
  *) second derivative

Default thresholds:
density: 1.000000e-15
   zeta: 2.220446e-16

Functional has 22 external parameters:
idx         value     name description
  0  1.000000e+00   _pp[0] pp0
  1  1.000000e+00   _pp[1] pp1
  2  1.000000e+00   _pp[2] pp2
  3  3.109100e-02    _a[0] a0
  4  1.554500e-02    _a[1] a1
  5  1.688700e-02    _a[2] a2
  6  2.137000e-01 _alpha1[0] alpha10
  7  2.054800e-01 _alpha1[1] alpha11
  8  1.112500e-01 _alpha1[2] alpha12
  9  7.595700e+00 _beta1[0] beta10
 10  1.411890e+01 _beta1[1] beta11
 11  1.035700e+01 _beta1[2] beta12
 12  3.587600e+00 _beta2[0] beta20
 13  6.197700e+00 _beta2[1] beta21
 14  3.623100e+00 _beta2[2] beta22
 15  1.638200e+00 _beta3[0] beta30
 16  3.366200e+00 _beta3[1] beta31
 17  8.802600e-01 _beta3[2] beta32
 18  4.929400e-01 _beta4[0] beta40
 19  6.251700e-01 _beta4[1] beta41
 20  4.967100e-01 _beta4[2] beta42
 21  1.709921e+00    _fz20 fz20
