Update read_input_item_output.cpp

Author: sunliang98

source/source_io/module_parameter/read_input_item_output.cpp

@@ -156,15 +156,19 @@ In molecular dynamics calculations, the output frequency is controlled by out_fr
         item.annotation = ">0 output density matrix DM(k) for each k-point";
         item.category = "Output information";
         item.type = R"(Boolean \[Integer\](optional))";
-        item.description = R"(Whether to output the density matrix for each k-point into files in the folder OUT.${suffix}. The files are named as:
-* For gamma only case:
- * nspin = 1 and 4: dm_nao.csr;
- * nspin = 2: dms1_nao.csr and dms2_nao.csr for the two spin channels.
-* For multi-k points case:
- * nspin = 1 and 4: dmk1_nao.csr, dmk2_nao.csr, ...;
- * nspin = 2: dmk1s1_nao.csr... and dmk1s2_nao.csr... for the two spin channels.
+        item.description = R"(Whether to output the density matrix for each k-point into files in the folder OUT.${suffix}. For current develop versions, out_dmk writes *_nao.txt files and includes a g{istep} index in the file name:
+    * For gamma only case:
+     * nspin = 1 and 4: dmg1_nao.txt;
+     * nspin = 2: dms1g1_nao.txt and dms2g1_nao.txt for the two spin channels.
+    * For multi-k points case:
+     * nspin = 1 and 4: dmk1g1_nao.txt, dmk2g1_nao.txt, ...;
+     * nspin = 2: dmk1s1g1_nao.txt... and dmk1s2g1_nao.txt... for the two spin channels.
+
+    Here, g{istep} denotes the geometry/step index in the output file name.
 
-[NOTE] In the 3.10-LTS version, the parameter is named out_dm and the file names are SPIN1_DM and SPIN2_DM, etc.)";
+    [NOTE] Version difference (develop vs 3.10-LTS):
+    * In develop, out_dmk supports both gamma-only and multi-k-point density-matrix output.
+    * In 3.10-LTS, the corresponding keyword is out_dm, and the output files are SPIN1_DM and SPIN2_DM, etc.)";
         item.default_value = "False";
         item.unit = "";
         item.availability = "Numerical atomic orbital basis";