Fixed abs bug in bravais_lattice + added method

When constructing the last unit vector in 2D, the sanity check was wrong because of usage of abs instead of std::abs.

Added method energy_on_bz_path_2 that returns the energy *matrix* at each k point on a given path instead of the eigenvalues of this matrix. The name of the function should be changed (to energy_matrix_on_bz_path?)

Renaming energies_on_bz_path_2 to energy_matrix_on_bz_path

pytriqs/lattice/lattice_tools.pyx

@@ -27,6 +27,7 @@ cdef extern from "triqs/lattice/tight_binding.hpp" namespace "triqs::gf" :
     pair [array[double,ONE],array[double,TWO]]  dos_c "dos" (tight_binding & TB, size_t nkpts, size_t neps)
     pair [array[double,ONE],array[double,ONE]]  dos_patch_c "dos_patch" (tight_binding & TB, array_view[double,TWO] & triangles, size_t neps, size_t ndiv)
     array_view[double,TWO] energies_on_bz_path_c "energies_on_bz_path" (tight_binding & TB, tqa_vector[double] & K1, tqa_vector[double] &  K2, size_t n_pts)
+    array_view[complex,THREE] energy_matrix_on_bz_path_c "energy_matrix_on_bz_path" (tight_binding & TB, tqa_vector[double] & K1, tqa_vector[double] &  K2, size_t n_pts)
     array_view[double,TWO] energies_on_bz_grid_c "energies_on_bz_grid" (tight_binding & TB, size_t n_pts)
 
 cdef class BravaisLattice :
@@ -104,6 +105,10 @@ def energies_on_bz_path ( TightBinding TB, K1, K2, n_pts) :
     """ """
     return energies_on_bz_path_c (deref(TB._c), tqa_vector[double](K1), tqa_vector[double] (K2), n_pts).to_python()  
 
+def energy_matrix_on_bz_path ( TightBinding TB, K1, K2, n_pts) : 
+    """ """
+    return energy_matrix_on_bz_path_c (deref(TB._c), tqa_vector[double](K1), tqa_vector[double] (K2), n_pts).to_python()  
+
 def energies_on_bz_grid ( TightBinding TB, n_pts) : 
     """ """ 
     return energies_on_bz_grid_c (deref(TB._c), n_pts).to_python() 

pytriqs/lattice/tight_binding.py

@@ -20,14 +20,14 @@
 #
 ################################################################################
 
-__all__ = ['BravaisLattice', 'TightBinding', 'dos', 'dos_patch', 'energies_on_bz_grid', 'energies_on_bz_path',
+__all__ = ['BravaisLattice', 'TightBinding', 'dos', 'dos_patch', 'energies_on_bz_grid', 'energies_on_bz_path', 'energy_matrix_on_bz_path',
            'hopping_stack', 'TBLattice']
 
 from lattice_tools import BravaisLattice as BravaisLattice
 from lattice_tools import TightBinding as TightBinding
 from lattice_tools import dos_patch as dos_patch_c
 from lattice_tools import dos as dos_c
-from lattice_tools import energies_on_bz_grid, energies_on_bz_path, hopping_stack
+from lattice_tools import energies_on_bz_grid, energies_on_bz_path, hopping_stack, energy_matrix_on_bz_path
 from pytriqs.dos import DOS
 import numpy
 

test/triqs/gfs/test_gf_triqs.cpp

@@ -5,6 +5,7 @@ using namespace triqs::arrays;
 #define TEST(X) std::cout << BOOST_PP_STRINGIZE((X)) << " ---> "<< (X) <<std::endl<<std::endl;
 #include <triqs/gfs/local/fourier_matsubara.hpp> 
 #include<fstream>
+#include <stdexcept>
 #define TEST(X) std::cout << BOOST_PP_STRINGIZE((X)) << " ---> "<< (X) <<std::endl<<std::endl;
 
 void print_to_file(std::string const s, gf<imtime> const & gt){

triqs/lattice/bravais_lattice_and_brillouin_zone.cpp

@@ -64,6 +64,7 @@ namespace lattice {
     uy(2) = 1;
     uy = cross_product(units_(0, _), units_(1, _));
     delta = sqrt(dot(uy, uy));
+    using std::abs;
     if (abs(delta) < almost_zero) TRIQS_RUNTIME_ERROR << "Bravais Lattice : the 2 vectors of unit are not independent : " << units__;
     units_(2, _) = uy / delta;
     break;

triqs/lattice/tight_binding.cpp

@@ -64,6 +64,19 @@ namespace lattice {
   return eval;
  }
 
+ //------------------------------------------------------
+ array<dcomplex, 3> energy_matrix_on_bz_path(tight_binding const& TB, k_t const& K1, k_t const& K2, int n_pts) {
+  auto TK = fourier(TB);
+  int norb = TB.lattice().n_orbitals();
+  int ndim = TB.lattice().dim();
+  array<dcomplex, 3> eval(norb,norb,n_pts);
+  k_t dk = (K2 - K1) / double(n_pts), k = K1;
+  for (int i = 0; i < n_pts; ++i, k += dk) {
+   eval(range(),range(),i) = TK(k(range(0, ndim)))();
+  }
+  return eval;
+ }
+
  //------------------------------------------------------
  array<double, 2> energies_on_bz_grid(tight_binding const& TB, int n_pts) {
 

triqs/lattice/tight_binding.hpp

@@ -93,6 +93,7 @@ namespace lattice {
  std::pair<array<double, 1>, array<double, 1>> dos_patch(tight_binding const& TB, const array<double, 2>& triangles, int neps,
                                                          int ndiv);
  array<double, 2> energies_on_bz_path(tight_binding const& TB, k_t const& K1, k_t const& K2, int n_pts);
+ array<dcomplex, 3> energy_matrix_on_bz_path(tight_binding const& TB, k_t const& K1, k_t const& K2, int n_pts);
  array<double, 2> energies_on_bz_grid(tight_binding const& TB, int n_pts);
 }
 }