add tddft gradient example

examples/27-tddft_grad.py

@@ -0,0 +1,57 @@
+#!/usr/bin/env python
+# Copyright 2021-2024 The PySCF Developers. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+###################################
+#  Example of TDDFT gradient
+###################################
+
+import pyscf
+import gpu4pyscf
+from gpu4pyscf import tdscf
+
+
+atom ='''
+O       0.0000000000    -0.0000000000     0.1174000000
+H      -0.7570000000    -0.0000000000    -0.4696000000
+H       0.7570000000     0.0000000000    -0.4696000000
+'''
+
+mol = pyscf.M(atom=atom, basis='def2-tzvpp')
+
+xc = 'b3lyp'
+mf = gpu4pyscf.dft.RKS(mol, xc=xc)
+mf.grids.level = 5
+mf.kernel() # -76.4666495331835
+
+# Compute TDDFT and TDA excitation energy
+print('------------------- TDDFT -----------------------------')
+td = mf.TDDFT().set(nstates=5)
+assert td.device == 'gpu'
+td.lindep=1.0E-6
+e_tddft = td.kernel()[0] # [ 7.51061148  9.42243504  9.76601005 11.74384344 13.5974535 ]
+print('The gradient of first TDDFT excitation energy by GPU4PySCF')
+g = td.nuc_grad_method()
+g.kernel()
+"""
+"""
+
+print('------------------- TDA -----------------------------')
+td = mf.TDA().set(nstates=5)
+assert td.device == 'gpu'
+e_tda = td.kernel()[0] # [ 7.53380573  9.42804505  9.81320363 11.78176645 13.62814473]
+print('The gradient of first TDA excitation energy by GPU4PySCF')
+g = td.nuc_grad_method()
+g.kernel()
+