利用Matlab从第一性原理计算软件Siesta读取和生成能带图

Siesta关于E-k关系计算结果保存于systemlabel.bands文件内，故Matlab程序只需要读取此文档即可。经笔者测试，在siesta-2.0.2与siesta-3.2版本内均可完美运行。

function sband( filename, E_range)
%sband('systemlabel.bands',[RangeOfBandEnergy])
%Read the file 'systemlabel.bands' and plot the band structure from siesta.
%The first argument is a must, while the E_range is of your own choice.
%Edited by JackyTu, July 29, 2014.
%Please contact tuxingchen@pku.edu.cn

fid=fopen(filename);
frewind(fid);

% -------------------- Read --------------------
E_fermi=fscanf(fid,'%f',1);
kmin=fscanf(fid,'%f',1);
kmax=fscanf(fid,'%f',1);
Emin=fscanf(fid,'%f',1);
Emax=fscanf(fid,'%f',1);
nband=fscanf(fid,'%d',1);
spin=fscanf(fid,'%d',1);
k_num=fscanf(fid,'%d',1);

if(nargin<2)
    E_range=[Emin,Emax];
end

kp=zeros(k_num,1);
e_data=zeros(nband*spin,k_num);
for i=1:k_num
    kp(i)=fscanf(fid,'%f',1);
    e_data(:,i)=fscanf(fid,'%f',nband*spin);
end

E_k=zeros(nband,k_num,2);
if spin==2
    E_k(:,:,1)=e_data(1:nband,:);
    E_k(:,:,2)=e_data((nband+1):end,:);
else
    E_k(:,:,1)=e_data;
end

n=fscanf(fid,'%d',1);
fgetl(fid);
for j=1:n
    str=fgetl(fid);
    str_out=strsplit(strtrim(str));
    xtick(j)=str2double(str_out{1});
    xtickLabel{j}=str_out{2}(2:end-1);
end

fclose(fid);

% -------------------- Plot --------------------
figure;
if spin==2
    subplot(1,2,1);
    hold on;
    for ii=1:nband
        plot(kp,E_k(ii,:,1)-E_fermi,'b');
    end
    for jj=2:n-1
        plot([xtick(jj),xtick(jj)],ylim,'k')
    end
    set(gca, 'xtick', xtick);
    set(gca, 'xticklabel', xtickLabel);
    ylabel('E-E_F(eV)');
    axis([xtick(1),xtick(end),E_range]);
    plot(xlim,[0,0],'--k');
    hold off;
    
    subplot(1,2,2);
    hold on;
    for ii=1:nband
        plot(kp,E_k(ii,:,2)-E_fermi,'r');
    end
    for jj=2:n-1
        plot([xtick(jj),xtick(jj)],ylim,'k')
    end
    set(gca, 'xtick', xtick);
    set(gca, 'xticklabel', xtickLabel);
    ylabel('E-E_F(eV)');
    axis([xtick(1),xtick(end),E_range]);
    plot(xlim,[0,0],'--k');
    hold off;
else
    hold on;
    for ii=1:nband
        plot(kp,E_k(ii,:,1)-E_fermi,'b');
    end
    for jj=2:n-1
        plot([xtick(jj),xtick(jj)],ylim,'k')
    end
    set(gca, 'xtick', xtick);
    set(gca, 'xticklabel', xtickLabel);
    ylabel('E-E_F(eV)');
    axis([xtick(1),xtick(end),E_range]);
    plot(xlim,[0,0],'--k');
    hold off;    
end
end

下面是附有运行sband函数后的效果图（此处计算体系为BCC-Fe）：