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dft_tools/doc/overview.rst

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TRIQS in a nutshell
===================
TRIQS is a toolbox containing **ready-to-use applications**, **python modules** as well as **C++ libraries** aimed at physicists in the field of quantum interacting systems.
Applications
------------
Interface to Wien2k for LDA+DMFT calculation
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TRIQS allows you to turn band-structure calculations obtained from the Wien2k package to inputs to full-fledged LDA+DMFT calculations in a few lines!
[example here]
To learn more, see <link>
Solvers for impurity models
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TRIQS comes with powerful numerical solvers for quantum impurity models.
[example here]
To learn more, see <link>
Python modules
--------------
Green's functions
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
With TRIQS, the manipulation of Green's functions is made easy: construction of Green's functions in frequency and time domains (imaginary and real), Fourier transforms, visualization, tail computation...
.. runblock:: python
# Import the Green's functions
from pytriqs.gf.local import GfImFreq, iOmega_n, inverse
# Create the Matsubara-frequency Green's function and initialize it
gw = GfImFreq(indices = [1], beta = 50, n_points = 1000, name = "imp")
gw <<= inverse( iOmega_n + 0.5 )
# Create an imaginary-time Green's function and plot it
gt = GFBloc_ImTime(Indices = [1], Beta = 50)
gt <<= InverseFourier(gw)
#from pytriqs.plot.mpl_interface import oplot
#oplot(g, '-o', x_window = (0,10))
print gt(0.5)
To learn more, see <link>
Lattice tools
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
With TRIQS, build a tight-binding model on any lattice in a few lines, and extract its density of states, dispersion...
[example here]
.. runblock:: python
print 2+2 # this will give output
To learn more, see <link>
C++ libraries
-------------
Monte-Carlo library
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Set up a Monte-Carlo simulation in a few lines: you write the configuration, moves and measures, while TRIQS takes care of the Metropolis algorithm and parallelization of the code.
.. compileblock::
#include <iostream>
#include <triqs/utility/callbacks.hpp>
#include <triqs/mc_tools/mc_generic.hpp>
// the configuration: a spin, the inverse temperature, the external field
struct configuration {
int spin; double beta, h;
configuration(double beta_, double h_) : spin(-1), beta(beta_), h(h_) {}
};
// a move: flip the spin
struct flip {
configuration & config;
flip(configuration & config_) : config(config_) {}
double attempt() { return std::exp(-2*config.spin*config.h*config.beta); }
double accept() { config.spin*= -1; return 1.0; }
void reject() {}
};
// a measurement: the magnetization
struct compute_m {
configuration & config;
double Z, M;
compute_m(configuration & config_) : config(config_), Z(0), M(0) {}
void accumulate(double sign) { Z += sign; M += sign * config.spin; }
void collect_results(boost::mpi::communicator const &c) {
double sum_Z, sum_M;
boost::mpi::reduce(c, Z, sum_Z, std::plus<double>(), 0);
boost::mpi::reduce(c, M, sum_M, std::plus<double>(), 0);
if (c.rank() == 0) {
std::cout << "Magnetization: " << sum_M / sum_Z << std::endl << std::endl;
}
}
};
int main(int argc, char* argv[]) {
// initialize mpi
boost::mpi::environment env(argc, argv);
boost::mpi::communicator world;
// greeting
if (world.rank() == 0) std::cout << "Isolated spin" << std::endl;
// prepare the MC parameters
int N_Cycles = 500000;
int Length_Cycle = 10;
int N_Warmup_Cycles = 1000;
std::string Random_Name = "";
int Random_Seed = 374982 + world.rank() * 273894;
int Verbosity = (world.rank() == 0 ? 2 : 0);
// construct a Monte Carlo loop
triqs::mc_tools::mc_generic<double> SpinMC(N_Cycles, Length_Cycle, N_Warmup_Cycles,
Random_Name, Random_Seed, Verbosity);
// parameters of the model
double beta = 0.3;
double field = 0.5;
// construct configuration
configuration config(beta, field);
// add moves and measures
SpinMC.add_move(flip(config), "flip move");
SpinMC.add_measure(compute_m(config), "magnetization measure");
// Run and collect results
SpinMC.start(1.0, triqs::utility::clock_callback(600));
SpinMC.collect_results(world);
return 0;
}
To learn more, see <link>
Array library
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Create, manipulate and store powerful multi-dimensional arrays:
.. highlight:: c
.. compileblock::
#include <triqs/arrays.hpp>
using triqs::arrays::array;
int main(){
array<double,1> A(20);
}
To learn more, see <link>
Expression library: CLEF
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Write mathematical expressions in a seamless and computationally efficient way:
.. compileblock::
#include <triqs/clef.hpp>
int main () {
triqs::clef::placeholder <1> x_;
auto e1 = cos(2*x_+1);
auto e2 = abs(2*x_-1);
auto e3 = floor(2*x_-1);
auto e4 = pow(2*x_+1,2);
}
To learn more, see <link>