gen_kpts.m

function [kpts, kpath_loc, kpath] = gen_kpts(kstart,kend,kpath,numpts,varargin)

% only option for a third input argument is a file to write the kpts to,
% this file is written in a format that works with postw90.x

% only do relative coords for the moment?

% each row of kstart and kend define endpoints of a path in kspace
% the start and end are assumed to be the same, up to periodicity
% this means the distance is set to 0 between these points when plotting,
% even if they are not technically the same point.

% numpts is the number of points on each path between the fixed points

% kpath is a string of points in the set {G,L,X,K}, should be equal to the
% number of paths+1, labels are assumed to occur at every transition from
% one path to the next, plus one at the start and one at the end.
%check / fix
% kL = [0.50000  0.50000 0.5000];
% kG = [0.00000  0.00000 0.0000];
% kX = [0.50000 -0.50000 0.0000];
% kK = [0.37500 -0.37500 0.0000];

n = size(kstart,1);

% build paths

% A = zeros(n,3);
% for k = 1:n
%     switch upper(kpath(k))
%         case {'G'}
%             A(k,:) = kG;
%         case {'L'}
%             A(k,:) = kL;
%         case {'K'}
%             A(k,:) = kK;
%         case {'X'}      
%             A(k,:) = kX;
%         otherwise
%             disp('invalid input')
%             break;
%     end            
% end
m = size(kstart,1);
total_kpts = m*(numpts + 2);
kpath_loc = zeros(m+1,1);

kline = linspace(0,1,numpts+2);
kpath_loc(1) = 1;
kpts = repmat(1-kline(:),1,3).*repmat(kstart(1,:),numpts+2,1) + ...
    repmat(kline(:),1,3).*repmat(kend(1,:),numpts+2,1);
kpath_loc(2) = size(kpts,1);
for k = 2:n
    temp = repmat(1-kline(:),1,3).*repmat(kstart(k,:),numpts+2,1) + ...
        repmat(kline(:),1,3).*repmat(kend(k,:),numpts+2,1);
    kpts = [kpts; temp];
    kpath_loc(k+1) = size(kpts,1);
end

kpath = upper(kpath);

% do file i/o

if nargin > 2
    fname = varargin{1};
    fid = fopen(fname,'w+');
    fprintf(fid,'kpt list generated by MATLAB\n');
    fprintf(fid,'crystal\n'); % only relative coords here for the moment
    fprintf(fid,'%i\n',total_kpts);
    temp = [(1:total_kpts)' kpts];
    fprintf(fid,'%d %7.5f %7.5f %7.5f\n',temp');
    fclose(fid);
end
    
    
    
% This is used for generating the path for QE nscf calculation
if nargin > 3
    fname = varargin{2};
    fid = fopen(fname,'w+');
    fprintf(fid,'kpt list generated by MATLAB\n');
    fprintf(fid,'K_POINTS {crystal}\n');
    fprintf(fid,'%i\n',total_kpts);
    wgts = ones(total_kpts,1)*1./total_kpts;
    temp = [kpts wgts];
    fprintf(fid,'%7.5f %7.5f %7.5f %7.5f\n',temp');
    fclose(fid);
end 
 
    
    
end