rename and update doc

Author: maki49

docs/advanced/input_files/input-main.md

@@ -420,6 +420,7 @@
     - [pexsi\_zero\_thr](#pexsi_zero_thr)
   - [Linear Response TDDFT](#linear-response-tddft)
     - [xc\_kernel](#xc_kernel)
+    - [lr\_init\_xc\_kernel](#lr_init_xc_kernel)
     - [lr\_solver](#lr_solver)
     - [lr\_thr](#lr_thr)
     - [nocc](#nocc)
@@ -3921,10 +3922,10 @@ Currently supported: `RPA`, `LDA`, `PBE`, `HSE`, `HF`.
 
 - **Type**: String
 - **Description**: The method to initalize the xc kernel. 
-  - "from_chg_groundstate": Calculate xc kerenel ($f_\text{xc}$) from the ground-state charge density.
-  - "file": Read the xc kernel $f_\text{xc}$ on grid from the provided files. The following words should be the paths of ".cube" files, where the first 3 (spin-aa, spin-ab and spin-bb) will be read in. The parameter [xc_kernel](#xc_kernel) will be invalid. Now only LDA-type kernel is supproted as the potential will be calculated by directly multiplying the transition density.
-  - "from_chg_file": Calculate fxc from the charge density read from the provided files. The following words should be the paths of ".cube" files, where the first [nspin]($nspin) files will be read in. 
-- **Default**: "from_chg_groundstate"
+  - "default": Calculate xc kerenel ($f_\text{xc}$) from the ground-state charge density.
+  - "file": Read the xc kernel $f_\text{xc}$ on grid from the provided files. The following words should be the paths of ".cube" files, where the first 1 (*[nspin](#nspin)==1*) or 3 (*[nspin](#nspin)==2*, namely spin-aa, spin-ab and spin-bb) will be read in. The parameter [xc_kernel](#xc_kernel) will be invalid. Now only LDA-type kernel is supproted as the potential will be calculated by directly multiplying the transition density.
+  - "from_charge_file": Calculate fxc from the charge density read from the provided files. The following words should be the paths of ".cube" files, where the first [nspin]($nspin) files will be read in. 
+- **Default**: "default"
 
 ### lr_solver
 

source/module_io/read_input_item_tddft.cpp

@@ -318,9 +318,9 @@ void ReadInput::item_lr_tddft()
             for (int i = 0; i < count; i++) { ifxc.push_back(item.str_values[i]); }
             };
         item.reset_value = [](const Input_Item& item, Parameter& para) {
-            if (para.input.lr_init_xc_kernel.empty()) { para.input.lr_init_xc_kernel.push_back("from_chg_groundstate"); }
+            if (para.input.lr_init_xc_kernel.empty()) { para.input.lr_init_xc_kernel.push_back("default"); }
             };
-        sync_stringvec(input.lr_init_xc_kernel, para.input.lr_init_xc_kernel.size(), "from_chg_groundstate");
+        sync_stringvec(input.lr_init_xc_kernel, para.input.lr_init_xc_kernel.size(), "default");
         this->add_item(item);
     }
     {

source/module_io/test/read_input_ptest.cpp

@@ -417,7 +417,7 @@ TEST_F(InputParaTest, ParaRead)
     EXPECT_EQ(param.inp.nocc, param.inp.nbands);
     EXPECT_EQ(param.inp.nvirt, 1);
     EXPECT_EQ(param.inp.xc_kernel, "LDA");
-    EXPECT_EQ(param.inp.lr_init_xc_kernel[0], "from_chg_groundstate");
+    EXPECT_EQ(param.inp.lr_init_xc_kernel[0], "default");
     EXPECT_EQ(param.inp.lr_solver, "dav");
     EXPECT_DOUBLE_EQ(param.inp.lr_thr, 1e-2);
     EXPECT_FALSE(param.inp.lr_unrestricted);

source/module_lr/potentials/pot_hxc_lrtd.h

@@ -19,7 +19,7 @@ namespace LR
         /// constructor for exchange-correlation kernel
         PotHxcLR(const std::string& xc_kernel, const ModulePW::PW_Basis& rho_basis,
             const UnitCell& ucell, const Charge& chg_gs/*ground state*/, const Parallel_Grid& pgrid,
-            const SpinType& st = SpinType::S1, const std::vector<std::string>& lr_init_xc_kernel = { "from_chg_groundstate" });
+            const SpinType& st = SpinType::S1, const std::vector<std::string>& lr_init_xc_kernel = { "default" });
         ~PotHxcLR() {}
         void cal_v_eff(double** rho, const UnitCell& ucell, ModuleBase::matrix& v_eff, const std::vector<int>& ispin_op = { 0,0 });
         const int& nrxx = nrxx_;

source/module_lr/potentials/xc_kernel.cpp

@@ -44,7 +44,7 @@ LR::KernelXC::KernelXC(const ModulePW::PW_Basis& rho_basis,
     }
 
 #ifdef USE_LIBXC
-    if (lr_init_xc_kernel[0] == "from_chg_file")
+    if (lr_init_xc_kernel[0] == "from_charge_file")
     {
         assert(lr_init_xc_kernel.size() >= 2);
         double** rho_for_fxc;