| In the theoretical study of the intermolecular interaction,CCSD?T?/CBS method can provide us with accurate calculation results,but because its calculation amount is proportional to O2N7?O is the number of occupied orbital,N is the number of basis functions?,it is very difficult in systems of more than 50 atoms.In 2013,the research group of Frank Neese proposed an approximation which domain based localized natural orbital?DLPNO?[C.Riplinger,Frank Neesea.J.Chem.Phys.138,034106?2013?],and formed some methods such as DLPNO-CCSD?T?and DLPNO-MP2.In recent years,however,a large number of studies have shown that DLPNO-CCSD?T?is directly applied to the calculation of intermolecular interaction energy,its calculation result is not ideal.In the high level correction?HLC?calculation of the DLPNO-CCSD?T?/CBS,we use the energy difference between DLPNO-CCSD?T?and DLPNO-MP2 to effectively offset the DLPNO approximation error.Among the three DLPNO approximate precision including Tight PNO,Normal PNO and Loose PNO,Tight PNO is the best standard for calculating the intermolecular interaction energy,at the same time,we maintain the consistency of the truncation parameters in DLPNO-CCSD?T?and DLPNO-MP2 calculations,so we proposed a DLPNO-CCSD?T?/CBS method of DLPNO error reduced.The accuracy and efficiency of DLPNO-CCSD?T0?and DLPNO-CCSD?T1?are further studied[75-77].We used the dateset including S22,HSG,HBC6 and NBC10 which were constructed C.David Sherrill research group to evaluate the calculation accuracy of DLPNO-CCSD?T?/CBS method.The results show that compared with the CCSD?T?/CBS method,the root mean square deviation?rmsd?of DLPNO-CCSD?T0?/CBS is 0.11 kcal/mol,and the maximum error?max?is 0.37kcal/mol.We provide an effective numerical procedure using DLPNO-CCSD?T?method for the accurate calculation of the intermolecular interaction energy,which is of great significance for the study of the interaction between molecules in medium and large systems. |
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