Added test for CAS fragmentation and screened interactions in benzene.

examples/ewf/molecules/36-crpa-cas-screening.py

@@ -0,0 +1,45 @@
+import pyscf.gto
+import pyscf.scf
+import pyscf.cc
+import pyscf.mcscf
+import vayesta.ewf
+from vayesta.misc import molecules
+
+mol = pyscf.gto.Mole()
+mol.atom = molecules.arene(6)
+mol.basis = 'cc-pVDZ'
+mol.output = 'pyscf.out'
+mol.build()
+
+mf = pyscf.scf.RHF(mol).density_fit()
+mf.kernel()
+
+ncas = (4,4)
+
+# Reference CASCI
+mycasci = pyscf.mcscf.CASCI(mf, *ncas)
+mycasci.kernel()
+
+# Equivalent CAS calculation with bare interactions
+casci_bare = vayesta.ewf.EWF(mf, bath_options=dict(bathtype="dmet"), screening=None, solver="FCI")
+with casci_bare.cas_fragmentation() as f:
+    f.add_cas_fragment(*ncas)
+casci_bare.kernel()
+
+# CAS calculation with cRPA screening
+casci_crpa = vayesta.ewf.EWF(mf, bath_options=dict(bathtype="dmet"), screening="crpa", solver="FCI")
+with casci_crpa.cas_fragmentation() as f:
+    f.add_cas_fragment(*ncas)
+casci_crpa.kernel()
+
+# CAS calculation with mRPA screening
+casci_mrpa = vayesta.ewf.EWF(mf, bath_options=dict(bathtype="dmet"), screening="mrpa", solver="FCI")
+with casci_mrpa.cas_fragmentation() as f:
+    f.add_cas_fragment(*ncas)
+casci_mrpa.kernel()
+
+print("E(HF)=                              %+16.8f Ha" % mf.e_tot)
+print("ΔE(CASCI)=                          %+16.8f Ha" % (mycasci.e_tot-mf.e_tot))
+print("ΔE(Emb. CASCI, bare interactions)=  %+16.8f Ha  (diff= %+.8f Ha)" % (casci_bare.e_tot-mf.e_tot, casci_bare.e_tot-mycasci.e_tot))
+print("ΔE(Emb. CASCI, cRPA screening)=     %+16.8f Ha  (diff= %+.8f Ha)" % (casci_crpa.e_tot-mf.e_tot, casci_crpa.e_tot-mycasci.e_tot))
+print("ΔE(Emb. CASCI, mRPA screening)=     %+16.8f Ha  (diff= %+.8f Ha)" % (casci_mrpa.e_tot-mf.e_tot, casci_mrpa.e_tot-mycasci.e_tot))