1(*
2 Copyright (C) 2017 M.A.L. Marques
3               2019 Susi Lehtola
4
5 This Source Code Form is subject to the terms of the Mozilla Public
6 License, v. 2.0. If a copy of the MPL was not distributed with this
7 file, You can obtain one at http://mozilla.org/MPL/2.0/.
8*)
9
10(* type: gga_exc *)
11(* prefix:
12  gga_c_pbe_vwn_params *params;
13
14  assert(p->params != NULL);
15  params = (gga_c_pbe_vwn_params * )(p->params);
16*)
17
18$include "lda_c_vwn.mpl"
19$ifdef gga_c_pbe_params
20params_a_beta  := 0.06672455060314922:
21params_a_gamma := (1 - log(2))/Pi^2:
22params_a_BB    := 1:
23$endif
24
25mgamma := params_a_gamma:
26mbeta  := (rs, t) -> params_a_beta:
27BB     := params_a_BB:
28
29tp   := (rs, z, xt) -> tt(rs, z, xt):
30
31(* Equation (8) *)
32A := (rs, z, t) ->
33  mbeta(rs, t)/(mgamma*(exp(-f_vwn(rs, z)/(mgamma*mphi(z)^3)) - 1)):
34
35(* Equation (7) *)
36f1 := (rs, z, t) -> t^2 + BB*A(rs, z, t)*t^4:
37f2 := (rs, z, t) -> mbeta(rs, t)*f1(rs, z, t)/(mgamma*(1 + A(rs, z, t)*f1(rs, z, t))):
38
39fH := (rs, z, t) -> mgamma*mphi(z)^3*log(1 + f2(rs, z, t)):
40
41f_pbe  := (rs, z, xt, xs0, xs1) ->
42  f_vwn(rs, z) + fH(rs, z, tp(rs, z, xt)):
43
44f  := (rs, z, xt, xs0, xs1) -> f_pbe(rs, z, xt, xs0, xs1):
45
46