02065nas a2200169   4500008004100000022001400041245013600055210006900191260007100260300001400331490000600345520135700351100002701708700001801735700001601753856012601769       2013                        eng d  a1549-961800aPerformance of the EOMIP-CCSD(2) method for determining the structure and properties of doublet radicals: a benchmark investigation0 aPerformance of the EOMIPCCSD2 method for determining the structu  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcOCT  a4313-43310 v93 a<p>We present a benchmark study on the performance of the EOMIP-CCSD(2) method for computation of structure and properties of doublet radicals. The EOMIP-CCSD(2) method is a second-order approximation to the standard EOMIP-CCSD method. By retaining the black box nature of the standard EOMIP-CCSD method and adding favorable N-5 scaling, the EOMIP-CCSD(2) method can become the method of choice for predicting the structure and spectroscopic properties of large doublet radicals. The EOMIP-CCSD(2) method overcomes the typical problems associated with the standard single reference ab initio treatment of doublet radicals. We compare our results for geometries and harmonic vibrational frequencies with those obtained using the standard EOMIP-CCSD method, as well as unrestricted Hartree-Fock (UHF)- and restricted open-shell Hartree-Fock (ROHF)-based single-reference coupled-cluster and second order many-body perturbation theory (MBPT(2)) methods. The effect of the basis set on the quality of the results has been studied using a hierarchy of Dunning's correlation-consistent aug-cc-pVXZ (X = D, T, Q) basis sets. Numerical results show that the EOMIP-CCSD(2) method, despite its N-5 scaling, gives better agreement with experimental results, compared to the UHF- and ROHF-based MBPT(2), as well as the single-reference coupled-cluster methods.</p>1 aDutta, Achintya, Kumar1 aVaval, Nayana1 aPal, Sourav  uhttps://library.ncl.res.in/content/performance-eomip-ccsd2-method-determining-structure-and-properties-doublet-radicals-0