Redirect to dftd3 and dftd4 package (#7)

* Abandon the pyscf-dftd3 extension. Redirect to dftd3 and dftd4 native interfaces

* Update README and exmples

Author: sunqm

README.md

@@ -1,24 +1,35 @@
 DFT-D3 interface
 ================
 
-2021-02-27
+pyscf-dftd3 extension is deprecated. It is recommended to use the newest DFTD3
+and DFTD4 interfaces hosted at https://github.com/dftd3/simple-dftd3 and
+https://github.com/dftd4/dftd4 . They can be installed via pypi packages
 
-* Version 0.1
-
-Install
--------
-* Install to python site-packages folder
 ```
-pip install git+https://github.com/pyscf/dftd3
+pip install dftd3 dftd4
 ```
 
-* Install in a custom folder for development
+dftd3 package provides a drop-in replacement of pyscf.dftd3.itrf. For example
+
 ```
-git clone https://github.com/pyscf/dftd3 /home/abc/local/path
+from pyscf import gto
+import dftd3.pyscf as d3
+
+mol = gto.M(
+    atom = ''' O    0.00000000    0.00000000   -0.11081188
+               H   -0.00000000   -0.84695236    0.59109389
+               H   -0.00000000    0.89830571    0.52404783 ''',
+    basis = 'cc-pvdz')
+
+mf = d3.energy(mol.RHF())
+print(mf.kernel())
 
-# Set pyscf extended module path
-echo 'export PYSCF_EXT_PATH=/home/abc/local/path:$PYSCF_EXT_PATH' >> ~/.bashrc
+mf.Gradients()
+mf.kernel()
 ```
 
-You can find more details of extended modules in the document
-[extension modules](http://pyscf.org/install.html#extension-modules)
+See also discussions in https://github.com/pyscf/dftd3/issues/3
+and the instructions for dftd3
+https://dftd3.readthedocs.io/en/latest/api/pyscf.html
+and dftd4
+https://dftd4.readthedocs.io/en/latest/reference/pyscf.html

examples/00-hf_with_dftd3.py

@@ -9,7 +9,7 @@
 
 from pyscf import gto
 from pyscf import scf
-from pyscf import dftd3
+import dftd3.pyscf as d3
 
 mol = gto.Mole()
 mol.atom = ''' O    0.00000000    0.00000000   -0.11081188
@@ -18,6 +18,8 @@
 mol.basis = 'cc-pvdz'
 mol.build()
 
-mf = dftd3.dftd3(scf.RHF(mol))
+mf = d3.energy(scf.RHF(mol))
 print(mf.kernel()) # -75.99396273778923
 
+mf.Gradients()
+mf.kernel()

pyscf/dftd3/__init__.py

@@ -16,7 +16,16 @@
 # Author: Qiming Sun <osirpt.sun@gmail.com>
 #
 
-__version__ = '0.0.1'
+__version__ = '0.0.2'
 
-from pyscf.dftd3 import itrf
-from pyscf.dftd3.itrf import dftd3, grad
+import warnings
+
+warnings.warn('''
+pyscf-dftd3 extension is deprecated. It is recommended to use the newest DFTD3
+and DFTD4 interfaces hosted at https://github.com/dftd3/simple-dftd3 and
+https://github.com/dftd4/dftd4 . They can be installed via pypi packages
+
+pip install dftd3 dftd4
+
+See also discussions in https://github.com/pyscf/dftd3/issues/3
+''')