1 ////////////////////////////////////////////////////////////////////////////////
2 //
3 // Copyright (c) 2008 The Regents of the University of California
4 //
5 // This file is part of Qbox
6 //
7 // Qbox is distributed under the terms of the GNU General Public License
8 // as published by the Free Software Foundation, either version 2 of
9 // the License, or (at your option) any later version.
10 // See the file COPYING in the root directory of this distribution
11 // or <http://www.gnu.org/licenses/>.
12 //
13 ////////////////////////////////////////////////////////////////////////////////
14 //
15 // RSHFunctional.h
16 //
17 ////////////////////////////////////////////////////////////////////////////////
18 //
19 // Range-separated hybrid functional (RSH)
20 // J.H.Skone et al. Phys. Rev. B93, 235106 (2016)
21 // RSH is defined by alpha_RSH, beta_RSH, mu_RSH
22 // sigma = alpha_RSH * rho(r,r') * erf(r-r')/(r-r') +
23 //         beta_RSH * rho(r,r') * erfc(r-r')/(r-r') +
24 //         (1 - alpha_RSH) * Vx_LR(r,mu_RSH) +
25 //         (1 - beta_RSH) * Vx_SR(r,mu_RSH)
26 // The HSE functional is obtained using alpha_RSH=0, beta_RSH=0.25, mu_RSH=0.11
27 // Heyd et al.,   J. Chem. Phys. 118, 8207 (2003)
28 // Heyd et al.,   J. Chem. Phys. 120, 7274 (2004)
29 // Krukau et al., J. Chem. Phys. 125, 224106 (2006)
30 //
31 ////////////////////////////////////////////////////////////////////////////////
32 
33 #ifndef RSHFUNCTIONAL_H
34 #define RSHFUNCTIONAL_H
35 
36 #include "XCFunctional.h"
37 #include <vector>
38 
39 class RSHFunctional : public XCFunctional
40 {
41   const double x_coeff_, c_coeff_;
42   const double alpha_RSH_, beta_RSH_, mu_RSH_;
43   const double omega; // == mu_RSH
44 
45   // vectors common to all GGA exchange functionals
46   std::vector<double> _exc, _exc_up, _exc_dn;
47   std::vector<double> _vxc1, _vxc1_up, _vxc1_dn, _vxc2, _vxc2_upup, _vxc2_updn,
48     _vxc2_dnup, _vxc2_dndn;
49   std::vector<double> _grad_rho[3], _grad_rho_up[3], _grad_rho_dn[3];
50 
51   void RSH_exchange(const double rho, const double grad,
52   const double a_ex, const double w, double *ex, double *vx1, double *vx2);
53 
54   void gcor2(double a, double a1, double b1, double b2,
55   double b3, double b4, double rtrs, double *gg, double *ggrs);
56 
57   void PBE_correlation(const double rho, const double grad,
58   double *ec, double *vc1, double *vc2);
59 
60   void PBE_correlation_sp(const double rho_up, const double rho_dn,
61   const double grad_up, const double grad_dn, const double grad, double *ec,
62   double *vc1_up, double *vc1_dn, double *vc2);
63 
64   void approximateIntegral(const double omega_kF, const double Hs2,
65   const double D_term, const double dHs2_ds, double *appInt,
66   double *dAppInt_ds, double *dAppInt_dkF);
67 
68   void RSH_enhance(const double s_inp, const double kF,
69   const double w, double *fx, double *dfx_ds, double* dfx_dkf);
70 
71   public:
72 
73   // constructor
74   RSHFunctional(const std::vector<std::vector<double> > &rhoe,
75                 double alpha_RSH, double beta_RSH, double mu_RSH);
76 
isGGA()77   bool isGGA() const { return true; }
78 
79   // return the name of the functional
name()80   std::string name() const { return "RSH"; }
81 
82   void setxc(void);
83 };
84 
85 #endif
86