Abstract
In order to perform practical electron correlation calculations, the local unitary transformation (LUT) scheme at the spin-free infinite-order Douglas-Kroll-Hess (IODKH) level [J. Seino and H. Nakai, J. Chem. Phys. 136, 244102 (2012); and ibid. 137, 144101 (2012)], which is based on the locality of relativistic effects, has been combined with the linear-scaling divide-and-conquer (DC)-based Hartree-Fock (HF) and electron correlation methods, such as the second-order Mo̸ller-Plesset (MP2) and the coupled cluster theories with single and double excitations (CCSD). Numerical applications in hydrogen halide molecules, (HX)n (X = F, Cl, Br, and I), coinage metal chain systems, Mn (M = Cu and Ag), and platinum-terminated polyynediyl chain, trans,trans-{(p-CH3C6H4)3P}2(C6H5)Pt(C≡C)4Pt(C6H5){(p-CH3C6H4)3P}2, clarified that the present methods, namely DC-HF, MP2, and CCSD with the LUT-IODKH Hamiltonian, reproduce the results obtained using conventional methods with small computational costs. The combination of both LUT and DC techniques could be the first approach that achieves overall quasi-linear-scaling with a small prefactor for relativistic electron correlation calculations.
Highlights
An alternative approach, namely, two-component relativistic theory, has attracted considerable attention because this theory produces only electronic-state information
The local unitary transformation (LUT) scheme can be combined with the efficient evaluation scheme for the Coulomb and exchange interactions such as the fast multipole method (FMM)44,45 because the twoelectron NR interaction is adopted as the long range electronelectron interaction
The numerical assessments of the LUT scheme indicated that the unitary transformation for one-center integrals with/without Coulombic two-center ones could be important because multi-center two-electron integrals with atomic unitary transformation would incorrectly describe the behavior in electron-electron interactions
Summary
Two-component relativistic theory, has attracted considerable attention because this theory produces only electronic-state (or large-component) information. We have proposed an accurate and efficient scheme, termed local unitary transformation (LUT), for twocomponent relativistic calculations at the one-40 and twoparticle spin-free infinite-order DKH (IODKH) level.. The DC-correlation method uses the molecular orbital (MO) information from the DCSCF method and the energy density analysis (EDA) technique.59 He and Merz have independently developed the DC-SCF method using the HF scheme (DC-HF) code, and used it to calculate realistic closed-shell proteins.. The DC method offers an advantage over the other fragmented-based linear-scaling treatments, in that it requires no artificial prediction related to the position of the spins and/or charges The reason for this is that the distribution of electrons in the system under consideration is uniformly settled by the common Fermi level, which is important for the accurate description of large π -conjugated systems.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
