fix(io): add space separators in out_mat_l format string (#7454)

When the number of atoms exceeds 150, the columns in Lx/Ly/Lz.dat
output files become indistinguishable because the %4d format fields
are not separated by spaces.

Fixes #6907

Author: mintleaf84

source/source_io/module_hs/cal_pLpR.cpp

@@ -273,9 +273,9 @@ void ModuleIO::AngularMomentumCalculator::kernel(
     // il and jl are indexes of the angular momentum,
     // iz and jz are indexes of the zeta functions
     // im and jm are indexes of the magnetic quantum numbers.
-    std::string fmtstr = "%4d%4d%4d%4d%4d%4d%4d%4d%4d%4d%4d%4d%4d";
-    fmtstr += "%" + std::to_string(precision*2) + "." + std::to_string(precision) + "e";
-    fmtstr += "%" + std::to_string(precision*2) + "." + std::to_string(precision) + "e\n";
+    std::string fmtstr = "%4d %4d %4d %4d %4d %4d %4d %4d %4d %4d %4d %4d %4d";
+    fmtstr += " %" + std::to_string(precision*2) + "." + std::to_string(precision) + "e";
+    fmtstr += " %" + std::to_string(precision*2) + "." + std::to_string(precision) + "e\n";
     FmtCore fmt(fmtstr);
 
     // placeholders