correct extended -> external

Author: kirk0830

docs/advanced/input_files/input-main.md

@@ -1065,7 +1065,7 @@ calculations.
 ### xc_exch_ext
 
 - **Type**: Integer Real ...
-- **Description**: Customized parameterization on the exchange part of XC functional. The first value should be the LibXC ID of the original functional, and latter values are extended parameters. Default values are those of Perdew-Burke-Ernzerhof (PBE) functional. For more information on LibXC ID of functionals, please refer to [LibXC](https://libxc.gitlab.io/functionals/). For parameters of functionals of interest, please refer to the source code of LibXC, such as PBE functional interface in LibXC: [gga_x_pbe.c](https://gitlab.com/libxc/libxc/-/blob/7.0.0/src/gga_x_pbe.c).
+- **Description**: Customized parameterization on the exchange part of XC functional. The first value should be the LibXC ID of the original functional, and latter values are external parameters. Default values are those of Perdew-Burke-Ernzerhof (PBE) functional. For more information on LibXC ID of functionals, please refer to [LibXC](https://libxc.gitlab.io/functionals/). For parameters of functionals of interest, please refer to the source code of LibXC, such as PBE functional interface in LibXC: [gga_x_pbe.c](https://gitlab.com/libxc/libxc/-/blob/7.0.0/src/gga_x_pbe.c).
 - **Default**: 101 0.8040 0.2195149727645171
 - **Note**:
   1. Solely setting this keyword will take no effect on XC functionals. One should also set `dft_functional` to corresponding functional to apply the customized parameterization. For example, if you want to use the PBE functional with customized parameters, you should set `dft_functional` to `GGA_X_PBE+GGA_C_PBE` and `xc_exch_ext` to `101 0.8040 0.2195149727645171`.
@@ -1075,7 +1075,7 @@ calculations.
 ### xc_corr_ext
 
 - **Type**: Integer Real ...
-- **Description**: Customized parameterization on the correlation part of XC functional. The first value should be the LibXC ID of the original functional, and latter values are extended parameters. Default values are those of Perdew-Burke-Ernzerhof (PBE) functional. For more information on LibXC ID of functionals, please refer to [LibXC](https://libxc.gitlab.io/functionals/). For parameters of functionals of interest, please refer to the source code of LibXC, such as PBE functional interface in LibXC: [gga_c_pbe.c](https://gitlab.com/libxc/libxc/-/blob/7.0.0/src/gga_c_pbe.c).
+- **Description**: Customized parameterization on the correlation part of XC functional. The first value should be the LibXC ID of the original functional, and latter values are external parameters. Default values are those of Perdew-Burke-Ernzerhof (PBE) functional. For more information on LibXC ID of functionals, please refer to [LibXC](https://libxc.gitlab.io/functionals/). For parameters of functionals of interest, please refer to the source code of LibXC, such as PBE functional interface in LibXC: [gga_c_pbe.c](https://gitlab.com/libxc/libxc/-/blob/7.0.0/src/gga_c_pbe.c).
 - **Default**: 130 0.06672455060314922 0.031090690869654895034 1.0
 - **Note**:
   1. Solely setting this keyword will take no effect on XC functionals. One should also set `dft_functional` to corresponding functional to apply the customized parameterization. For example, if you want to use the PBE functional with customized parameters, you should set `dft_functional` to `GGA_X_PBE+GGA_C_PBE` and `xc_corr_ext` to `130 0.06672455060314922 0.031090690869654895034 1.0`.

source/module_hamilt_general/module_xc/xc_functional_libxc.cpp

@@ -201,7 +201,7 @@ XC_Functional_Libxc::init_func(const std::vector<int> &func_id,
 		funcs.push_back({}); // create placeholder
 		xc_func_init(&funcs.back(), id, xc_polarized); // instantiate the XC term
 
-		// search for extended parameters
+		// search for external parameters
 		const std::vector<double> in_built_ext_params = in_built_xc_func_ext_params(id);
 		const std::vector<double> external_ext_params = external_xc_func_ext_params(id);
 		// for temporary use, I name their size as n1 and n2
@@ -221,12 +221,12 @@ XC_Functional_Libxc::init_func(const std::vector<int> &func_id,
 		const double* xc_func_ext_params = 
 			(n2 > 0) ? external_ext_params.data() : 
 			(n1 > 0) ? in_built_ext_params.data() :
-			nullptr; // nullptr if no extended parameters are found
+			nullptr; // nullptr if no external parameters are found
 
-		// if there are no extended parameters, do nothing, otherwise we set
+		// if there are no external parameters, do nothing, otherwise we set
 		if(xc_func_ext_params != nullptr)
 		{
-			// set the extended parameters
+			// set the external parameters
 			xc_func_set_ext_params(&funcs.back(), const_cast<double*>(xc_func_ext_params));
 		}
 	}

source/module_hamilt_general/module_xc/xc_functional_libxc.h

@@ -28,14 +28,14 @@ namespace XC_Functional_Libxc
     extern std::pair<int,std::vector<int>> set_xc_type_libxc(const std::string& xc_func_in);
 
     /**
-     * @brief instantiate the XC functional by its ID, and set the extended parameters if provided.
+     * @brief instantiate the XC functional by its ID, and set the external parameters if provided.
      * 
      * @param func_id libxc ID of functional, see https://libxc.gitlab.io/functionals/ for details
      * @param xc_polarized 0: unpolarized, 1: spin-polarized
      * @return std::vector<xc_func_type> 
      * 
      * @note the functionality of this method is extended by supporting the user-defined
-     *       extended parameters of xc. However, there are several functionals' extended 
+     *       external parameters of xc. However, there are several functionals' external 
      *       parameters are pre-defined in the code, which herein we call those are 
      *       "in-built" parameters. If the same functional ID is found in both in-built 
      *       and external parameters, the external parameters will overwrite the in-built ones.

source/module_parameter/input_parameter.h

@@ -654,7 +654,7 @@ struct Input_para
     bool exxace = true; // exxace, exact exchange for planewave basis, https://doi.org/10.1021/acs.jctc.6b00092
     bool exx_gamma_extrapolation = true; // gamma point extrapolation for exx, https://doi.org/10.1103/PhysRevB.79.205114
 
-    // ====   #Parameters (23.XC extended parameterization) ========
+    // ====   #Parameters (23.XC external parameterization) ========
     /*
      * the following two sets of parameters are for the XC parameterization.
      * The first element should be the LibXC id, to assign the analytical