A5008144836- Advanced Chemical Physics Studies
- Physics of Superconductivity and Magnetism
- Advanced NMR Techniques and Applications
- Spectroscopy and Quantum Chemical Studies
- Quantum and electron transport phenomena
- Machine Learning in Materials Science
- Image and Signal Denoising Methods
- Quantum, superfluid, helium dynamics
- Inorganic Fluorides and Related Compounds
- Mathematical Approximation and Integration
- Theoretical and Computational Physics
- Advanced Condensed Matter Physics
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Physical and Chemical Molecular Interactions
- Atomic and Molecular Physics
- Seismic Imaging and Inversion Techniques
- Electron and X-Ray Spectroscopy Techniques
- Catalytic Processes in Materials Science
- Catalysis and Oxidation Reactions
- Nuclear physics research studies
- Electron Spin Resonance Studies
- Advanced Image Fusion Techniques
- Plasma Diagnostics and Applications
- Nuclear Physics and Applications
- Quantum many-body systems
Max Planck Institute for Solid State Research
2017-2023
University of Cambridge
2019-2022
RIKEN Center for Computational Science
2021
Data61
2020
Commonwealth Scientific and Industrial Research Organisation
2020
The Dodd-Walls Centre for Photonic and Quantum Technologies
2020
University of Iowa
2020
Massey University
2020
King's College London
2020
University of Waterloo
2020
We present NECI, a state-of-the-art implementation of the Full Configuration Interaction Quantum Monte Carlo (FCIQMC) algorithm, method based on stochastic application Hamiltonian matrix sparse sampling wave function. The program utilizes very powerful parallelization and scales efficiently to more than 24 000 central processing unit cores. In this paper, we describe core functionalities NECI its recent developments. This includes capabilities calculate ground excited state energies,...
Transcorrelated methods provide an efficient way of partially transferring the description electronic correlations from ground-state wave function directly into underlying Hamiltonian. In particular, Dobrautz et al. [Phys. Rev. B 99, 075119 (2019)] have demonstrated that use momentum-space representation, combined with a nonunitary similarity transformation, results in Hubbard Hamiltonian possesses significantly more ``compact'' function, dominated by single Slater determinant. This...
We suggest an efficient method to resolve electronic cusps in structure calculations through the use of effective transcorrelated Hamiltonian. This Hamiltonian takes a simple form for plane wave bases, containing up two-body operators only, and its incurs almost no additional computational overhead compared that original apply this combination with full configuration interaction quantum Monte Carlo (FCIQMC) homogeneous electron gas. As projection technique, non-Hermitian nature does not...
Similarity transformation of the Hubbard Hamiltonian using a Gutzwiller correlator leads to non-Hermitian effective Hamiltonian, which can be expressed exactly in momentum-space representation, and contains three-body interactions. We apply this methodology study two-dimensional model with repulsive interactions near half-filling intermediate interaction strength regime ($U/t=4$). show that at optimal or correlator, similarity transformed has extremely compact right eigenvectors, sampled...
By expressing the electronic wavefunction in an explicitly correlated (Jastrow-factorized) form, a similarity-transformed effective Hamiltonian can be derived. The is non-Hermitian and contains three-body interactions. resulting ground-state eigenvalue problem solved projectively using stochastic configuration-interaction formalism. Our approach permits use of highly flexible Jastrow functions, which we show to achieving extremely high accuracy, even with small basis sets. Results are...
We propose a streamlined combination scheme of the transcorrelation (TC) and coupled cluster (CC) theory, which not only increases convergence rate with respect to basis set, but also extends applicability lowest order CC approximations strongly correlated regimes in three dimensional uniform electron gas (3D UEG). With correct physical insights built into correlator used TC, highly accurate ground state energies errors $\leq 0.001 $ a.u./electron relative state-of-the-art quantum Monte...
We demonstrate how similarity-transformed full configuration interaction quantum Monte Carlo (FCIQMC) based on the transcorrelated Hamiltonian can be applied to make highly accurate predictions for binding curve of beryllium dimer, marking first case study a molecular system with this method. In context, non-Hermitian Hamiltonian, resulting from similarity transformation Jastrow factor, serves purpose effectively address dynamic correlation beyond used basis set and thus allows obtaining...
A hyperbolic singularity in the wave function of s-wave interacting atoms is root problem for any accurate numerical simulation. Here, we apply transcorrelated method, whereby wave-function explicitly described by a two-body Jastrow factor, and then folded into Hamiltonian via similarity transformation. The resulting nonsingular eigenfunctions are approximated stochastic Fock-space diagonalization with energy errors scaling 1/M number M single-particle basis functions. performance method...
We propose a new approach to the use of Jastrow ansatz in calculation electron correlations, based on modification transcorrelated method Boys and Handy [Proc. R. Soc. London, Ser. A 309, 209 (1969)]. In this method, original orbital equation is replaced with general variational for reference wave function, whereas correlation factor remains same. The can be applied single determinant as well multideterminant one. For ansatz, we obtain Hartree-Fock type self-consistent optimization orbitals,...
Exact diagonalization expansions of Bose or Fermi gases with contact interactions converge very slowly due to a nonanalytic cusp in the wave function. Here we develop transcorrelated approach where is treated exactly and folded into many-body Hamiltonian similarity transformation that removes leading-order singularity. The resulting not Hermitian but can be numerically standard projection approach. smoothness function improves by at least one order thus convergence rate for ground-state...
We investigate the performance of newly developed variational transcorrelated (VTC) method (H. Luo, J. Chem. Phys. 133, 154109 (2010)) on overall optimisation multi-configuration Jastrow wave function. Similar to standard self consistent field methods, optimisations orbitals are realized by iterative unitary transformations, where skew-symmetric matrix elements determined using Newton-Raphson scheme. Third order density matrices introduced deal with three-body VTC potential. Test...
We have studied the performance of Boys and Handy's transcorrelated equation for Jastrow factors, without further approximations on integrals involved, using quantum Monte Carlo methods. Contrary to previous statements in literature, we observed no violation variational bounds. Our results agree very high accuracy with calculations various atoms small molecules. It should be mentioned that our findings are not direct contradiction Handy obtained 40 years ago. Instead their were slightly...
We investigate Nagaoka ferromagnetism in the two-dimensional Hubbard model with one hole using spin-adapted [$\text{SU}(2)$ conserving] full configuration interaction quantum Monte Carlo method. This methodology gives us access to ground-state energies of all possible spin states $S$ finite lattices, here obtained for lattices up 26 sites various strengths ($U$). The critical strength, ${U}_{c}$, at which transition occurs is determined each lattice and found be proportional size larger...
We have constructed the complete transcorrelated equation for homogeneous electron gases and investigated this on two- three-dimensional systems. Correct asymptotic behaviours of correlation factors can be easily obtained from equation, both long-range RPA type decay short-range spin dependent cusp conditions. The is solved numerically outcome energies agree very well with variational quantum Monte Carlo results. Possible simplifications calculations are discussed, where we find that factor...
We have studied various aspects concerning the use of hyperbolic wavelets and adaptive approximation schemes for wavelet expansions correlated wave functions. In order to analyze consequences reduced regularity function at electron–electron cusp, we first considered a realistic exactly solvable many-particle model in one dimension. Convergence rates expansions, with respect L2 H1 norms energy, were established this model. compare performance their extensions through refinement cusp region,...
Two-dimensional Hubbard lattices with two or three holes are investigated as a function of $U$ in the large-$U$ limit. In so-called Nagaoka limit (one-hole system at infinite $U$), it is known that model exhibits ferromagnetic ground state. Here, by means exact full configuration interaction quantum Monte Carlo simulations applied to periodic up 24 sites, we compute spin-spin correlation functions increasing $U$. The clearly demonstrate onset domains, centered on individual holes. overall...
We present a direct comparison of the exchange-only optimized effective potential ($x$-OEP) method, originating from density functional theory, with Hartree-Fock (HF) results for jellium slabs finite width, based on fully self-consistent calculations. The nonlocal character HF exchange causes coupling momentum parallel to slab surface perpendicular component orbitals. This in an entirely different energy-band structure close Fermi and terms bandwidth, as compared $x$-OEP structure. Good...
We present a multiscale treatment of electron correlations based on hyperbolic wavelet expansions Jastrow-type correlation functions. Wavelets provide hierarchical basis sets that can be locally adapted to the length- and energy-scales physical phenomena. Combined with tensor products local adaptive refinement near interelectron cusp, these bases enable sparse representations Jastrow factors. The computational efficiency wavelets in electronic structure calculations is demonstrated within...
We have studied an iterative perturbative approach to optimize Jastrow factors in quantum Monte Carlo calculations. For initial guess of the factor we construct a corresponding model Hamiltonian and solve first-order perturbation equation order obtain improved factor. This process is repeated until convergence. Two different types Hamiltonians been for both energy variance minimization. Our can be considered as alternative Newton’s method. Test calculations revealed same fast convergence...
Three-dimensional discrete tensor wavelets are applied to calculate wave functions of excess electrons solvated in polar liquids. Starting from the Hartree–Fock approximation for electron and linear response solute charge solvent, we have derived approximate free energy functional electrons. The orthogonal Coifman basis set is used minimize functions. scheme calculation properties singlet bipolaron formation. obtained results indicate that proposed algorithm fast rather efficient calculating...
With a transcorrelated Hamiltonian, we perform many body perturbation calculation on the uniform electron gas in high density regime. By using correlation factor optimized for single determinant Jastrow ansatz, second order energy is calculated as 1−ln2π2ln(rs)−0.05075. This already reproduces exact logarithmic term of random phase approximation (RPA) result, while constant roughly 7% larger than RPA one. The close agreement with method demonstrates that offers viable and potentially...
We present a perturbative treatment of Jastrow-type correlation factors which focus on an accurate description short-range correlations. Our approach is closely related to coupled cluster perturbation theory with the essential difference that we start from variational formulation for energy. Such kind especially suited multiscale bases, such as wavelets, provide sparse representations Jastrow factors. Envisaged applications in solid-state physics are confined many-particle systems electrons...
We present Hartree-Fock surface energies, work functions, and dipole barriers for a Jellium slab model at different electron densities widths. The fully self-consistent calculations take into account the nonlocal exchange coupling of momentum parallel to with perpendicular component orbitals. Typical oscillations due quantum-size effects have been observed. Our results provide lower upper bounds energy function semi-infinite jellium which can serve as benchmarks previously reported...