Abstract Highly correlated orbitals coupled with phonons in two-dimension are identified for paramagnetic and optically active boron vacancy hexagonal nitride by first principles methods which responsible recently observed detected magnetic resonance signal. Here, we report ab initio analysis of the electronic structure this center density matrix renormalization group Kohn-Sham functional theory methods. By establishing nature bright dark states as well position energy levels, provide a...

We have studied transition metal clusters from a quantum information theory perspective using the density-matrix renormalization group (DMRG) method. demonstrate competition between entanglement and interaction localization. also discuss application of configuration based dynamically extended active space procedure which significantly reduces effective system size accelerates speed convergence for complicated molecular electronic structures to great extent. Our results indicate importance...

The treatment of high‐dimensional problems such as the Schrödinger equation can be approached by concepts tensor product approximation. We present general techniques that used for optimization tasks and time‐dependent equations, connect them to already in many‐body quantum physics. Based on achievements from past decade, entanglement‐based methods—developed different perspectives purposes distinct communities matured provide a variety tools—can combined attack highly challenging chemistry....

We elaborate on the methodology of computing color centers in periodic and cluster models hBN. Using first-principles methods, we determined various optical properties nitrogen interstitial defect compared them to experimental results.

The accurate calculation of the (differential) correlation energy is central to quantum chemical description bond-formation and bond-dissociation processes. In order estimate quality single- multireference approaches for this purpose, various diagnostic tools have been developed. work, we elaborate on our previous observation [J. Phys. Chem. Lett.2012, 3, 3129] that one- two-orbital-based entanglement measures provide quantitative means assessment classification electron effects among...

We have studied the metal--insulator-like transition in pseudo-one-dimensional systems, i.e., lithium and beryllium rings, through ab initio density matrix renormalization group (DMRG) method. Performing accurate calculations for different interatomic distances using quantum information theory, we investigated changes occurring wave function between a metallic-like state an insulating built from free atoms. also discuss entanglement relevant excitations among molecular orbitals Li Be rings...

In this paper, we analyze the numerical aspects of inherent multireference density matrix renormalization group (DMRG) calculations on top periodic Kohn–Sham functional theory using complete active space approach. The potential framework is illustrated by studying hexagonal boron nitride nanoflakes embedding a charged single vacancy point defect revealing vertical energy spectrum with prominent character. We investigate consistency DMRG from perspective sample size, basis and selection...

The operator algebra of fermionic modes is isomorphic to that qubits, the difference between them twofold: embedding subalgebras corresponding mode subsets and multiqubit subsystems on one hand, parity superselection in case other. We discuss these two fundamental differences extensively, illustrate through Jordan--Wigner representation a coherent, self-contained, pedagogical way, from point view quantum information theory. Our perspective leads us develop useful new tools for treatment...

Abstract Point defect quantum bits in semiconductors have the potential to revolutionize sensing at atomic scales. Currently, vacancy-related defects are forefront of high spatial resolution and low-dimensional sensing. On other hand, it is expected that impurity-related structures may give rise new features could further advance low dimensions. Here, we study symmetric carbon tetramer clusters hexagonal boron nitride propose them as spin qubits for We utilize periodic-DFT chemistry...

We introduce transition operators that in a given basis of the single-site states many-body system have single nonvanishing matrix element and their correlation functions. show they fall into groups decay with same rate. The mutual information defined terms von Neumann entropy between two sites is these so-called generalized confirm numerically long-distance follows square most slowly decaying function. main advantage our procedure that, order to identify relevant physical processes, there...

The quantum mechanical description of the chemical bond is generally given in terms delocalized bonding orbitals, or, alternatively, correlations occupations localised orbitals. However, latter case, multiorbital were treated only two-orbital correlations, although structure far richer; and, case bonds established by more than two electrons, represent a natural point view. Here, for first time, we introduce true correlation theory, consisting framework handling toolbox measures, and...

Abstract Defect quantum bits (qubits) constitute an important emerging technology. However, it is necessary to explore new types of defects enable large-scale applications. In this article, we examine the potential magnesium-vacancy (MgV) in diamond operate as a qubit by computing key electronic- and spin properties with robust theoretical methods. We find that electronic structure MgV permits coexistence two loosely separated spin-states, where both can emerge ground state be interconverted...

Coupled cluster calculations are traditionally performed over Hartree-Fock reference orbitals (HF-CC methodology). However, in the literature it has been repeatedly raised whether use of a Kohn-Sham (KS-CC methodology) might result improved performance relative to HF-CC. In present study, we re-examine relation HF-CC and KS-CC methods by comparing results widely applied truncated CC (CCSD, CCSD(T), CCSDT) limit full configuration interaction (FCI), which serves as an undebatable point...

We present an alternative, memory-efficient, Schmidt decomposition-based description of the inherently bipartite restricted active space (RAS) scheme, which can be implemented effortlessly within density matrix renormalization group (DMRG) method via dynamically extended procedure. Benchmark calculations are compared against state-of-the-art results C2 and Cr2, notorious for their multireference character. Our ground excited states together with spectroscopic constants demonstrate that...

We theoretically derive and validate with large scale simulations a remarkably accurate power law scaling of errors for the restricted active space density matrix renormalization group (DMRG-RAS) method [J. Phys. Chem. A 126, 9709] in electronic structure calculations. This yields new extrapolation method, DMRG-RAS-X, which reaches chemical accuracy strongly correlated systems such as chromium dimer, dicarbon up to cc-pVQZ basis even complex FeMoco significantly lower computational demands...

We revisit the phase diagram of frustrated $s=1/2$ spin ladder with antiferromagnetic rung and diagonal couplings. In particular, we reexamine evidence for columnar dimer phase, which has been predicted from analytic treatment model claimed to be found in numerical calculations. By performing density-matrix renormalization-group (DMRG) calculations on long ladders, keeping a large number states within DMRG, carrying out careful scaling kept system size, calculate behavior order parameter as...

We study theoretically poly-diacetylene chains diluted in their monomer matrix. employ the density-matrix renormalization group method (DMRG) on finite to calculate ground state and low-lying excitations of corresponding Peierls--Hubbard-Ohno Hamiltonian which is characterized by electron transfer amplitude t0 between nearest neighbors, electron-phonon coupling constant \alpha, Hubbard interaction U, long-range V. treat lattice relaxation adiabatic limit, i.e., we polaronic distortions for...

Abstract Point defect qubits in semiconductors have demonstrated their outstanding capabilities for high spatial resolution sensing generating broad multidisciplinary interest. Hexagonal boron nitride (hBN) hosting point recently opened up new horizons quantum by implementing foils. The sensitivity of sensors hBN is currently limited the linewidth magnetic resonance signal, which broadened due to strong hyperfine couplings. Here, we report on a vacancy-related spin qubit with an inherently...

Recently, the correlation theory of chemical bond was developed, which applies concepts quantum information for characterization bonds, based on multiorbital correlations within molecule. Here, first time, we extend use this mathematical toolbox description electron-deficient bonds. We start by verifying textbook example a molecule with three-center two-electron namely, diborane(6). then show that is able to properly describe bonding situation in more exotic molecules have been synthesized...

We study the elementary excitations of a model Hamiltonian for $\ensuremath{\pi}$ electrons in polydiacetylene chains. In these materials, bare band gap is only half size observed single-particle and binding energy exciton 0.5 eV amounts to 20% gap. Therefore, exchange correlations due long-range Coulomb interaction require numerically exact treatment which we carry out using density-matrix renormalization group method. Employing both Hubbard-Ohno potential screened one dimension, reproduce...

The bonding mechanism of ethene to a nickel or palladium center is studied by the density matrix renormalization group algorithm, complete active space self-consistent field method, coupled cluster theory, and functional theory. Specifically, we focus on interaction between metal atom bis-ethene ligands in perpendicular parallel orientations. situation these structural isomers further scrutinized using energy decomposition analysis quantum information Our study highlights fact that when two...