Journal ArticleDOI
Third-order multireference perturbation theory: the n-electron valence state perturbation-theory approach.
TLDR
A formulation of the n-electron valence state perturbation theory (NEVPT) at the third order of perturbations is presented and the so-called strongly contracted variant of NEVPT, where only a subspace of the first-order interacting space is taken into account, is presented.Abstract:
A formulation of the n-electron valence state perturbation theory (NEVPT) at the third order of perturbation is presented. The present implementation concerns the so-called strongly contracted variant of NEVPT, where only a subspace of the first-order interacting space is taken into account. The resulting strongly contracted NEVPT3 approach is discussed in three test cases: (a) the energy difference between the 3B1 and 1A1 states of the methylene molecule, (b) the potential-energy curve of the N2 molecule ground state, and (c) the chromium dimer (Cr2) ground-state potential-energy profile. Particular attention is devoted to the last case where large basis sets comprising also h orbitals are adopted and where remarkable differences between the second- and third-order results show up.read more
Citations
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Journal ArticleDOI
Slow magnetization dynamics in a series of two-coordinate iron(II) complexes
Joseph M. Zadrozny,Mihail Atanasov,Mihail Atanasov,Aimee M. Bryan,Chun Yi Lin,Brian D. Rekken,Philip P. Power,Frank Neese,Jeffrey R. Long +8 more
TL;DR: In this paper, a series of two-coordinate complexes of iron(II) were prepared and studied for single-molecule magnet behavior, and the spin reversal barriers were fit by employing a sum of tunneling, direct, Raman and Orbach relaxation processes, resulting in spin reversal barrier of Ueff = 181, 146, 109, 104, and 43 cm−1 for 1−5, respectively.
Journal ArticleDOI
Second-order perturbation theory with a density matrix renormalization group self-consistent field reference function: theory and application to the study of chromium dimer
Yuki Kurashige,Takeshi Yanai +1 more
TL;DR: The DMRG-CASPT2/cc-pwCV5Z calculations were performed with a large (3d double-shell) active space consisting of 28 orbitals and addressed the problems of why the dissociation energy is largely overestimated by CASPT2, and also is oversensitive to the choice of the zeroth-order Hamiltonian.
Journal ArticleDOI
First principles approach to the electronic structure, magnetic anisotropy and spin relaxation in mononuclear 3d-transition metal single molecule magnets
Mihail Atanasov,Mihail Atanasov,Daniel Aravena,Elizaveta A. Suturina,Elizaveta A. Suturina,Eckhard Bill,Dimitrios Maganas,Frank Neese +7 more
TL;DR: In this paper, a self-contained introduction to electronic structure calculations for single molecule magnet properties is provided in conjunction with several contemporary case studies on diverse mononuclear 3d-transition metal complexes.
Journal ArticleDOI
New perspectives in multireference perturbation theory: the n-electron valence state approach
TL;DR: The n-electron valence state perturbation theory (NEVPT) as mentioned in this paper is a form of multireference perturbations theory which is based on a zero order reference wave function of CAS-CI type (complete active space configuration interaction) and characterized by the utilization of correction functions (zero order wavefunctions external to the CAS) of multi-ireference nature, obtained through the diagonalization of a suitable twoelectron model Hamiltonian in some well defined determinant spaces.
Journal ArticleDOI
A theoretical analysis of chemical bonding, vibronic coupling, and magnetic anisotropy in linear iron(II) complexes with single-molecule magnet behavior
TL;DR: In this article, the electronic structure and magnetic anisotropy of six complexes of high-spin FeII with linear FeX2 (X = C, N, O) cores, Fe[N(SiMe3)(Dipp)]2 (1), Fe[C(SiME3)3]2 (2), Fe [N(H)Ar′]2(3), Fe•N(Ar*]2,4,6-Pri2)2, Ar# = C6H3-2,6-(C6H2-2.
References
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Journal ArticleDOI
Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen
TL;DR: In this paper, a detailed study of correlation effects in the oxygen atom was conducted, and it was shown that primitive basis sets of primitive Gaussian functions effectively and efficiently describe correlation effects.
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The calculation of small molecular interactions by the differences of separate total energies. Some procedures with reduced errors
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Journal ArticleDOI
An efficient internally contracted multiconfiguration–reference configuration interaction method
TL;DR: In this article, a new internally contracted direct multiconfiguration-reference configuration interaction (MRCI) method is described which allows the use of much larger reference spaces than any previous MRCI method.