Ground State Properties Research Articles

A systematic study of the ground state properties of gold nuclei near the neutron drip line using HFB formalism

In this theoretical work, the ground state properties like binding energy per nucleon, two-neutron separation energy, two-neutron shell gap, neutron-pairing gap, neutron rms radii, proton rms radii, charge radii, neutron skin thickness and nucleon density distributions of odd-even and odd-odd gold isotopes (A165−265u) were systematically studied. Computations were performed for a wide mass range of gold nuclei, spanned from the proton-rich side to the neutron-rich side, following the Hartree-Fock-Bogoliubov theory. Based on this approach, the nuclear structure of gold isotopes lying up to the exotic neutron rich region where the experimental data are not available, was also investigated. Calculations, taking into account the UNEDF0 Skyrme effective interaction, reproduce the available experimental data and results of other nuclear model based estimations, such as the Relativistic-Continuum-Hartree-Bogoliubov theory and the Finite Range Droplet Models, reasonably well.

Qubit-Efficient Randomized Quantum Algorithms for Linear Algebra

We propose a class of randomized quantum algorithms for the task of sampling from matrix functions, without the use of quantum block encodings or any other coherent oracle access to the matrix elements. As such, our use of qubits is purely algorithmic and no additional qubits are required for quantum data structures. Our algorithms start from a classical data structure in which the matrix of interest is specified in the Pauli basis. For N×N Hermitian matrices, the space cost is log(N)+1 qubits and, depending on the structure of the matrices, the gate complexity can be comparable to state-of-the-art methods that use quantum data structures of up to size O(N2), when considering equivalent end-to-end problems. Within our framework, we present a quantum linear system solver that allows one to sample properties of the solution vector, as well as algorithms for sampling properties of ground states and Gibbs states of Hamiltonians. As a concrete application, we combine these subroutines to present a scheme for calculating Green’s functions of quantum many-body systems. Published by the American Physical Society 2024

Study of Shape Evolution and Ground State Properties of Even-Even Tellurium Isotopic Mass Chain by using Relativistic Hartree Bogoliubov framework

Study of Shape Evolution and Ground State Properties of Even-Even Tellurium Isotopic Mass Chain by using Relativistic Hartree Bogoliubov framework

Quantum Davidson algorithm for excited states

Excited state properties play a pivotal role in various chemical and physical phenomena, such as charge separation and light emission. However, the primary focus of most existing quantum algorithms has been the ground state, as seen in quantum phase estimation and the variational quantum eigensolver (VQE). Although VQE-type methods have been extended to explore excited states, these methods grapple with optimization challenges. In contrast, the quantum Krylov subspace (QKS) method has been introduced to address both ground and excited states, positioning itself as a cost-effective alternative to quantum phase estimation. However, conventional QKS methodologies depend on a pre-generated subspace through real or imaginary-time evolutions. This subspace is inherently expansive and can be plagued with issues like slow convergence or numerical instabilities, often leading to relatively deep circuits. Our research presents an economic QKS algorithm, which we term the quantum Davidson (QDavidson) algorithm. This innovation hinges on the iterative expansion of the Krylov subspace and the incorporation of a pre-conditioner within the Davidson framework. By using the residues of eigenstates to expand the Krylov subspace, we manage to formulate a compact subspace that aligns closely with the exact solutions. This iterative subspace expansion paves the way for a more rapid convergence in comparison to other QKS techniques, such as the quantum Lanczos. Using quantum simulators, we employ the novel QDavidson algorithm to delve into the excited state properties of various systems, spanning from the Heisenberg spin model to real molecules. Compared to the existing QKS methods, the QDavidson algorithm not only converges swiftly but also demands a significantly shallower circuit. This efficiency establishes the QDavidson method as a pragmatic tool for elucidating both ground and excited state properties on quantum computing platforms.

Iron(III) Carbene Complexes with Tunable Excited State Energies for Photoredox and Upconversion.

Substituting precious elements in luminophores and photocatalysts by abundant first-row transition metals remains a significant challenge, and iron continues to be particularly attractive owing to its high natural abundance and low cost. Most iron complexes known to date face severe limitations due to undesirably efficient deactivation of luminescent and photoredox-active excited states. Two new iron(III) complexes with structurally simple chelate ligands enable straightforward tuning of ground and excited state properties, contrasting recent examples, in which chemical modification had a minor impact. Crude samples feature two luminescence bands strongly reminiscent of a recent iron(III) complex, in which this observation was attributed to dual luminescence, but in our case, there is clear-cut evidence that the higher-energy luminescence stems from an impurity and only the red photoluminescence from a doublet ligand-to-metal charge transfer (2LMCT) excited state is genuine. Photoinduced oxidative and reductive electron transfer reactions with methyl viologen and 10-methylphenothiazine occur with nearly diffusion-limited kinetics. Photocatalytic reactions not previously reported for this compound class, in particular the C-H arylation of diazonium salts and the aerobic hydroxylation of boronic acids, were achieved with low-energy red light excitation. Doublet-triplet energy transfer (DTET) from the luminescent 2LMCT state to an anthracene annihilator permits the proof of principle for triplet-triplet annihilation upconversion based on a molecular iron photosensitizer. These findings are relevant for the development of iron complexes featuring photophysical and photochemical properties competitive with noble-metal-based compounds.

JLab spectral functions of argon in nuwro and their implications for MicroBooNE

The Short-Baseline Neutrino program in Fermilab aims to resolve the nature of the low-energy excess events observed in LSND and MiniBooNE, and analyze with unprecedented precision neutrino interactions with argon. These studies require a reliable estimate of neutrino cross sections, in particular for charged current quasielastic scattering (CCQE). Here, we report updates of the uro Monte Carlo generator that, most notably, bring the state-of-the-art spectral functions to model the ground state properties of the argon nucleus, and improve the accuracy of the cross sections at low energies by accounting for the effects of the nuclear Coulomb potential. We discuss these developments in the context of electron and neutrino interactions, by comparing updated uro predictions to experimental data from Jefferson Laboratory Hall A and MicroBooNE. The MicroBooNE CCQE-dominated data are described with the χ2 per degree of freedom of 0.7, compared with 1.0 in the local Fermi gas model. The largest improvement is observed for the angular distributions of the produced protons, where the χ2 reduces nearly by half. Being obtained using the axial form factor parametrization from MINERvA, our results indicate a consistency between the CCQE measurements in MINERvA and MicroBooNE. Published by the American Physical Society 2024

Singular limit of periodic metric grids

We investigate the asymptotic behavior of nonlinear Schrödinger ground states on d-dimensional periodic metric grids in the limit for the length of the edges going to zero. We prove that suitable piecewise–affine extensions of such states converge strongly in H1(Rd) to the corresponding ground states on Rd. As an application of such convergence results, qualitative properties of ground states and multiplicity results for fixed mass critical points of the energy on grids are derived. Moreover, we compare optimal constants in d-dimensional Gagliardo–Nirenberg inequalities on Rd and on grids. For L2-critical and supercritical powers, we show that the value of such constants on grids is strictly related to that on Rd but, contrary to Rd, constants on grids are not attained. The proofs of these results combine purely variational arguments with new Gagliardo–Nirenberg inequalities on grids.

Effect of the pairing types and pairing strength on the ground state properties of even and odd Mg isotopes

This study is an investigation of the effect of the pairing strength using different types of pairing (surface, volume and mixed surface–volume pairing) on the ground state properties of even and odd Mg isotopes. The Hartree–Fock–Bogoliubov (HFB) theory and two types of Skyrme forces, SKI3 and SLY6, were employed in our calculations. The pairing strength values are modified at each execution of the HFBTHO code to obtain the experimental values of binding energy for the investigated even and odd isotopes separately. Then a new formula for pairing strength for each even and odd isotope independently for all the pairing, surface, volume and mixed surface–volume types is developed by fitting the pairing strength values to the mass number. Based on the newly generated formulas for pairing strength, some of the calculated ground state properties are found to depend strongly on the pairing strength values and the pairing type also plays an essential role in providing accurate results.

Magnetic properties of the spin-1 J 1 − J 3 Heisenberg model on a triangular lattice

We study the spin-1 J 1 − J 3 Heisenberg model with antiferromagnetic nearest neighbors J 1 > 0 and the ferromagnetic third nearest neighbor J 3 < 0 for a triangular lattice. The ground-state and thermodynamic properties are evaluated under the Popov-Fedotov functional integral method and the Luttinger-Tisza procedure. Perturbation expansion of the auxiliary field around mean-field theory was carried out to investigate the effect of thermal fluctuations on ground state energy and sublattice magnetization. The results are compared with those of the spin wave approximation and other methods.

Machine learning nuclear orbital-free density functional based on Thomas–Fermi approach

Orbital-free density functional theory (DFT) is much more efficient than the orbital-dependent Kohn–Sham DFT due to the avoidance of the auxiliary one-body orbitals. The machine learning approach has been applied to build nuclear orbital-free DFT recently [Wu et al., Phys. Rev. C 105 (2022) L031303] and achieved more precise descriptions for nuclei than existing orbital-free DFTs. Here, improved machine learning nuclear orbital-free density functional is built by including the Thomas–Fermi approach as a basement. Performances of the functional are compared in detail with the ones based on the pure machine learning approach. It is found that with the Thomas–Fermi functional included, the machine-learning-based functional can achieve better performance in directly predicting the kinetic energies and in providing the ground-state properties by the self-consistent procedures.

On discrete ground states of rotating Bose–Einstein condensates

The ground states of Bose–Einstein condensates in a rotating frame can be described as constrained minimizers of the Gross–Pitaevskii energy functional with an angular momentum term. In this paper we consider the corresponding discrete minimization problem in Lagrange finite element spaces of arbitrary polynomial order and we investigate the approximation properties of discrete ground states. In particular, we prove a priori error estimates of optimal order in the L 2 L^2 - and H 1 H^1 -norm, as well as for the ground state energy and the corresponding chemical potential. A central issue in the analysis of the problem is the missing uniqueness of ground states, which is mainly caused by the invariance of the energy functional under complex phase shifts. Our error analysis is therefore based on an Euler–Lagrange functional that we restrict to certain tangent spaces in which we have local uniqueness of ground states. This gives rise to an error decomposition that is ultimately used to derive the desired a priori error estimates. We also present numerical experiments to illustrate various aspects of the problem structure.

Non-Kramers doublet ground state in a quaternary cubic compound PrRu2In2Zn18 investigated by ultrasonic measurements

Abstract We performed ultrasonic measurements on a quaternary cubic compound PrRu2In2Zn18 to explore the ground state properties derived from non-Kramers Γ3 doublet of Pr3+. PrRu2In2Zn18 is a quaternary derivative of the ternary compound PrRu2Zn20 that exhibits a structural phase transition at T S = 138 K. In PrRu2In2Zn18, the Zn atoms at the 16c site in PrRu2Zn20 are selectively replaced by In atoms. A monotonic increase was observed in the temperature dependence of elastic constants C L = (C 11 + 2C 12 + 4C 44)/3 and C T = (C 11–C 12 + C 44)/3 in the temperature range around T S to which an elastic softening was observed in (C 11 – C 12)/2 for PrRu2Zn20. The disappearance of the softening indicates that the structural transition in PrRu2Zn20 is suppressed by the substitution of Zn ions by In ones with a larger ionic radius. Alternatively, the C T of PrRu2In2Zn18 exhibits a precursor Curie-type elastic softening toward low temperatures being responsible for the non-Kramers Γ3 ground state. We discuss the ground state and the evolution of the elastic properties of the different single-crystal samples of PrRu2In2Zn18 grown under different conditions.

Exotic symmetry breaking properties of self-dual fracton spin models

Fracton codes host unconventional topological states of matter and are promising for fault-tolerant quantum computation due to their large coding space and strong resilience against decoherence and noise. In this paper, we investigate the ground-state properties and phase transitions of two prototypical self-dual fracton spin models—the tetrahedral Ising model and the fractal Ising model—which correspond to error-correction procedures for the representative fracton codes of type I and type II, the checkerboard code and the Haah's code, respectively, in the error-free limit. They are endowed with exotic symmetry-breaking properties that contrast sharply with the spontaneous breaking of global symmetries and deconfinement transition of gauge theories. To show these unconventional behaviors, which are associated with subdimensional symmetries, we construct and analyze the order parameters, correlators, and symmetry generators for both models. Notably, the tetrahedral Ising model acquires an extended semilocal ordering moment, while the fractal Ising model fits into a polynomial ring representation and leads to a fractal order parameter. Numerical studies combined with analytical tools show that both models experience a strong first-order phase transition with an anomalous L−(D−1) scaling, despite the fractal symmetry of the latter. Our paper provides a unique understanding of subdimensional symmetry breaking and makes an important step for studying quantum-error-correction properties of the checkerboard and Haah's codes. Published by the American Physical Society 2024

First-principles study on rare earth-based equiatomic quaternary Heusler alloys YbCoCrSb and YbCoTiSn: New candidates for spintronics

We have investigated the structural, mechanical, thermal, electronic, magnetic, and half-metallic properties of new Yb-based EQHAs such as YbCoCrSb and YbCoTiSn using first-principles calculations. We computed the ground state properties of different possible crystal structures and magnetic states. We also calculated their elastic constants and derived mechanical parameters, including bulk, shear, and Young's moduli, as well as Poisson's and Pugh ratios. The electronic structure of both EQHAs shows half-metallic behavior with a spin down band gap of 0.39 eV for YbCoCrSb and 0.30 eV for YbCoTiSn in the GGA-PBE scheme. The estimated total spin magnetic moment has a positive integer value, which is well in accordance with the Slater-Pauling rule of 18. Because of the nearly closed f orbital shell of the Yb atom, the total spin magnetic moment is mainly dependent on 3d transition metal atoms. These alloys exhibit TC > 300 K using the mean field approximation.

A study of U-isotope ground state properties with Covariant Energy Density Functional

Abstract In this paper we have systematically analyzed the ground state of uranium isotopes from 225 to 240. In our calculations, we used the covariant energy density functional of density dependent meson exchange interaction (DD-ME2) with separable pairing interaction (TMR). Using the multiple deformation constraint, we calculate the potential energy surface (PES) of the uranium isotopes for&amp;#xD;both even-even and even-odd nuclei with quadrupole and octupole deformation. By comparison with experimental data and Hartree-Fock-Bogoliubov calculations with Gogny D1S, the ground state of the uranium isotopes is always preferred to reflection-asymmetric deformation with our calculation.

Improved Carrier Separation and Recombination by Ferroelectric Polarization in the CuBiP2Se6/C2N Heterostructure: A Nonadiabatic Molecular Dynamics Study.

The rapid recombination of photogenerated carriers heavily restricts the photocatalytic efficiency. Here, we propose a new strategy to improve catalytic efficiency based on the ferroelectric van der Waals heterostructure (CuBiP2Se6/C2N). Combining density functional theory and the nonadiabatic molecular dynamics (NAMD) method, we have systematically analyzed the ground-state properties and carrier dynamics images in the CuBiP2Se6/C2N heterostructure. Our calculations showed that the ferroelectric polarization of CuBiP2Se6 provides the internal driving force for the photogenerated carriers separation. NAMD results demonstrate that the excited-state carrier transfer and recombination processes in the CuBiP2Se6/C2N are consistent with a type II mechanism. Meanwhile, constructing the ferroelectric heterostructure can effectively prolong the carrier lifetime, from ∼65.98 to ∼124.54 ps. Moreover, the high quantum efficiency and tunable band edge positions mean that the CuBiP2Se6/C2N heterostructure is an excellent potential candidate material for photocatalytic water splitting.

The structural, electronic, optical, and mechanical properties of carbon-based halides: An ab initio DFT approach

In the present work, we choose the carbon-based halides CX4 (X = Br, Cl) to conduct a study on the ground-state properties using first-principles calculations based on density functional theory. We provide a comparative study for bromide and chloride materials using standard generalized gradient approximation functionals. A total of 80 atoms have been simulated on a single unit cell. A direct bandgap energy of 3.28 (4.64) eV for X = Br (X = Cl) with Z–Z transition is found on the studied materials. According to our partial density of states plot, a hybridization of s orbitals on C and X atoms is observed. Metallic properties have also been identified. A low reflectivity of 6% (12%) has been measured, which presents excellent material absorption. Such a material is also determined to be brittle, based on the calculated Pugh’s ratio. The reflectivity (ductility) tends to increase as the X element increases down the Period Table. The negative Poisson’s ratio found also suggests that the materials could be used as an electrode for metal-ion (e.g., Li, K, and Na) batteries.

Optical, thermal and semiempirical study of Samarium bi-tartrate trihydrate

In this comprehensive study, we investigated the structure, optical, and thermal aspects of [Sm(C4H5O6)(C4H4O6)][3H2O], a samarium based metal-organic framework. Testing and exploring advanced semiempirical quantum models, we provide some insights into ground-state molecular properties within the solid metal-organic framework. The single-excitation configuration interaction approach within the spectroscopic method INDO/S-CIS was utilized in the computation of UV spectra, singlet, and triplet excited states for the uncoordinated organic component. We also exploited the established Judd-Ofelt theory to elucidate the spectroscopic properties, allowing us to predict various attributes, including absorption and luminescence traits. The inclusion of thermogravimetric analysis exposes a multifaceted thermal decomposition process. Moreover, this analysis was explored in the determination of activation energies associated with distinct stages of decomposition.

Probing the structural and electronic properties of MAX phases and their corresponding MXenes using first-principles calculations

Abstract This study delves into the theoretical exploration of the structural and electronic characteristics of 2D monolayer MXenes (M n + 1X n ) by the elimination of Al layers from their corresponding MAX-phases, M n + 1AX n (n = 1–3), through meticulous first-principles calculations. The study encompasses structural optimization and the determination of key ground state properties, including equilibrium lattice constants, energy (E 0), and volume (V 0) of both MXenes and their corresponding MAX phases. Consequently, we investigated the comparative study of the electronic properties of M n + 1AlC n (M = Ti, V, or Cr) (n = 1–3) and their MXenes for the first time by calculating the Bader charge analysis (MAX phase only) and the density of states (DOS). The analysis extends to the density of states and Bader charge assessments, facilitating a comprehensive comparison. Remarkably, the MXene monolayer showcases an elevated density of states at the Fermi level compared to its MAX phase counterpart. This disparity stems from the redistribution of 3d electrons near the Fermi level following the removal of Al layers, consequently enhancing electronic conductivity. Cohesive energy and formation energy calculations affirm the structural stability of these compounds. Furthermore, our computed values are meticulously cross-referenced with existing experimental and theoretical data, stimulating the reliability and significance of our findings.

First‐Principles Calculations to Investigate the Ground State, Mechanical Stability, Electronic Structure, and Optical Properties of Tl2SnX3 (X = S, Se, Te)

AbstractIn this work, the Density Functional Theory (DFT) analysis of the Tl2SnX3 series (X = S, Se, Te) is performed, and the ground states are confirmed by the calculation of the elastic constant Cij. Based on the DFT calculation, the Tl2SnX3 structures are direct‐gap semiconductors with bandgaps of 1.434, 1.181, and 0.907 eV, respectively. Chalcogen substitution significantly impacts their electronic structures, notably increasing the Density of States (DOS) width in the valence band from sulfur to tellurium, and shifting the dielectric function's real part, ε1(ω), toward lower energies. This change means that the optical activity and response to electric fields are better, with Tl2SnTe3 showing the best polarization response and light‐matter interaction abilities. Optical tests show that Tl2SnTe3 has very high optical absorption, peaking at ≈17 × 104 cm−1 along [010], and reflectivity levels above 90%, marking its suitability for high‐reflectivity applications. Moreover, loss energy function analysis also shows that Tl2SnTe3 has a strong electron loss resonance at lower energies, which means it has strong interactions with electrons.