Phase Boundary Code
D. Stanford
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/*
phase_diagram.cc
Description:
This code evaluates the gap equation integral and outputs a text file
that gives the coordinates in the U/t' plane (t=1) of the
antiferromagnetic/nonmagnetic phase boundary.
Compilation instructions:
Strip off the html commands and store the source in the file
grid.cpp. Under gcc then execute
g++ phase_diagram.cc -o phase_diagram
./phase_diagram
Copyright 2008 Douglas Stanford. The author grants permission
to copy, distribute and display this work in unaltered form, with
attribution to the author, for noncommercial purposes only. All other
rights, including commercial rights, are reserved to the author.
*/
#include <iostream>
#include <math.h>
#include <fstream>
#include <unistd.h>
//VARIABLES
float pi=3.14159265;
//FUNCTIONS
float GapEqn(float A,float B,float C);
void PlotUofd();
using namespace std;
int main(){
PlotUofd();
return 0;
}
float GapEqn(float A, float B, float C){
float dq1=0.01;
float counter=0;
for(float qx=-pi; qx<pi; qx+=dq1){
for(float qy=-pi; qy<pi; qy+=dq1){
counter+=(dq1*dq1)*((A+4*B*sin(qx)*sin(qy))/sqrt(4*C*C*(pow(cos(qx),2)+pow(cos(qy),2))+pow(A+4*B*sin(qx)*sin(qy),2)));
}
}
counter/=(pow(2*pi,2));
return(2*A/counter);
}
void PlotUofd(){
ofstream outfileU;
outfileU.open("U.txt");
for(float tprime=-1; tprime<=1; tprime+=.1){
outfileU<<tprime<<'\t'<<GapEqn(.0001,tprime,1)<<endl;
}
}
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