update comments in example

Author: jeanwsr

examples/dh/01-init.py

@@ -17,7 +17,7 @@
 #          Shirong Wang <srwang20@fudan.edu.cn>
 #
 
-"""Example: DFDH initialization — mol, SCF object, and to_dh conversion."""
+"""Example: DFDH initialization"""
 
 from pyscf import gto, dft
 from pyscf.dh import DFDH, to_dh
@@ -29,22 +29,25 @@
 
 print(f"B2PLYP via mol:   {mf.e_tot:.8f}")
 
-# 2. Init with converged KS SCF — reuses orbitals, skips SCF
+# 2. Init with converged KS SCF 
+# DFDH allows initialization mf_or_mol, but it only accepts and reuses mf 
+# when its xc exactly matches the DH's SCF part ("0.53*HF + 0.47*B88, 0.73*LYP" for B2PLYP)
+# It refuses to continue when SCF mismatches
 mf_ks = dft.KS(mol, xc="0.53*HF + 0.47*B88, 0.73*LYP").density_fit().run()
 mf = DFDH(mf_ks, xc="B2PLYP").run()
 print(f"B2PLYP via KS:    {mf.e_tot:.8f}")
 
-# For xDH — pre-converge B3LYPg SCF for XYG3 (Proc. Natl. Acad. Sci. 2009, 106 (13), 4963–4968.)
+# example for xDH — pre-converge B3LYPg SCF for XYG3 (Proc. Natl. Acad. Sci. 2009, 106 (13), 4963–4968.)
 mf_ks = dft.KS(mol, xc="B3LYPg").density_fit().run()
 mf = DFDH(mf_ks, xc="XYG3").run()
 print(f"XYG3 via B3LYPg:  {mf.e_tot:.8f}")
 
-# 3. to_dh — reuse when SCF matches 
+# 3. to_dh — reuse when SCF matches (the same as DFDH initialization)
 mf_ks = dft.KS(mol, xc="B3LYPg").density_fit().run()
 mf = to_dh(mf_ks, xc="XYG3").run()
 print(f"to_dh reuse XYG3: {mf.e_tot:.8f}")
 
-# to_dh — auto-convert when SCF mismatches 
+# to_dh also supports auto-convert when SCF mismatches 
 mf_ks = dft.KS(mol, xc="PBE0").density_fit().run()
 mf = to_dh(mf_ks, xc="B2PLYP").run()
 print(f"to_dh conv PBE0 -> B2PLYP: {mf.e_tot:.8f}")