A first-principles Quantum Monte Carlo study of two-dimensional (2D) GaSe

Wines, Daniel; Saritas, Kayahan; Ataca, Can

doi:10.1063/5.0023223

Cited by 29 publications

(21 citation statements)

References 110 publications

(149 reference statements)

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“…It is also noted that lattice constants of AFM ordering are slightly smaller than FM ordering for every functional and U values. As expected, PBE tends to overestimate the lattice constant, LDA tends to underestimate, and SCAN (meta-GGA) can achieve highly accurate lattice constants, as demonstrated in previous works 35,64 . For this reason, we used the fixed lattice constant and atomic positions obtained with SCAN (for FM ordering) for all subsequent DMC and DFT+U spin-orbit calculations (discussed later in this section).…”

Section: Resultssupporting

confidence: 79%

The intrinsic ferromagnetism of two-dimensional (2D) MnO$_2$ revisited: A many-body Quantum Monte Carlo and DFT+U study

Wines,

Saritas,

Ataca

2021

Preprint

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is one of the few predicted two-dimensional (2D) ferromagnets that has been experimentally synthesized and is commercially available. It is known that the Ising-like spin Hamiltonian is not valid for 2D systems, as a consequence of the Mermin-Wagner theorem, which states that magnetic order in a 2D material cannot persist unless magnetic anisotropy (MA) is present and perpendicular to the plane. Previous computational studies have predicted the magnetic ordering and Curie temperature of 2D MnO 2 with DFT+U (Density Funtional Theory + Hubbard U correction), with the results having a strong dependence on the Hubbard U parameter. Diffusion Monte Carlo (DMC) is a correlated electronic structure method that has had demonstrated success for the electronic and magnetic properties of a variety of 2D and bulk systems since it has a weaker dependence on the starting Hubbard parameter and density functional. In this study, we used DMC and DFT+U to calculate the magnetic properties of monolayer MnO 2 . We found that the ferromagnetic ordering is more favorable than antiferromagnetic and determined a statistical bound on the magnetic exchange parameter (J). In addition, we performed spin-orbit MA energy calculations using DFT+U and using our DMC and DFT+U parameters along with the analytical model of Torelli and Olsen 1 , we estimated an upper bound of 28.8 K for the critical temperature of MnO 2 . These QMC results intend to serve as an accurate theoretical benchmark, necessary for the realization and development of future 2D magnetic devices. These results also demonstrate the need for accurate methodologies to predict magnetic properties of correlated 2D materials.

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Section: Resultssupporting

confidence: 79%

The intrinsic ferromagnetism of two-dimensional (2D) MnO$_2$ revisited: A many-body Quantum Monte Carlo and DFT+U study

Wines,

Saritas,

Ataca

2021

Preprint

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“…The obtained observables such as binding energies, excitation gaps, vibrational frequencies have also been accurate and agreed very well with CCSD(T) results as well as with experiment [7]. In addition, DMC and related methods are applicable to much larger systems such as periodic models of solids in both insulating and metallic states, 2D materials, and systems with Email address: hzhou23@ncsu.edu (Haihan Zhou) other effective interactions such ultracold atoms and beyond [8,9,10,11,12].…”

Section: Introductionsupporting

confidence: 73%

A quantum Monte Carlo study of systems with effective core potentials and node nonlinearities

et al. 2022

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“…40 Even though DFT has led to transformative changes in our understanding of materials and chemistry and typically yields good results for ground state properties in 3D, especially lattice constants, it can yield widely varying results for the properties of 2D materials, such as lattice parameters and band gaps, depending upon the functional employed. Recent studies of 2D materials have shown that DFT consistently overestimates interlayer binding energies between 2D monolayers 41 and predicts lattice parameters that routinely differ from experimental ones by several percent. 42,43 In contrast, Diffusion Monte Carlo (DMC), a real-space, many-body quantum Monte Carlo method, routinely predicts lattice constants within 1% and band gaps to within 10% of their experimental values for the same materials.…”

Section: Introductionmentioning

confidence: 98%

“…42,43 In contrast, Diffusion Monte Carlo (DMC), a real-space, many-body quantum Monte Carlo method, routinely predicts lattice constants within 1% and band gaps to within 10% of their experimental values for the same materials. [41][42][43][44] It is worth emphasizing that DMC obtains such high-accuracy results for all properties within a single, consistent framework with few approximations; moreover, the approximations can be systematically improved upon because of the variational nature of DMC. In contrast, obtaining accurate DFT results of different properties often necessitates using a different functional for each and every property, which substantially reduces the predictive power of such calculations.…”

Section: Introductionmentioning

confidence: 99%

A Combined First Principles Study of the Structural, Magnetic, and Phonon Properties of Monolayer CrI$_{3}$

Staros,

Hu,

Tiihonen

et al. 2021

Preprint

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The first magnetic 2D material discovered, monolayer (ML) CrI3, is particularly fascinating due to its ground state ferromagnetism. Yet, because monolayer materials are difficult to probe experimentally, much remains unresolved about ML CrI3's structural, electronic, and magnetic properties. Here, we leverage Density Functional Theory (DFT) and high-accuracy Diffusion Monte Carlo (DMC) simulations to predict lattice parameters, magnetic moments, and spin-phonon and spinlattice coupling of ML CrI3. We exploit a recently developed surrogate Hessian DMC line search technique to determine CrI3's monolayer geometry with DMC accuracy, yielding lattice parameters in good agreement with recently-published STM measurements-an accomplishment given the ∼ 10% variability in previous DFT-derived estimates depending upon the functional. Strikingly, we find previous DFT predictions of ML CrI3's magnetic spin moments are correct on average across a unit cell, but miss critical local spatial fluctuations in the spin density revealed by more accurate DMC. DMC predicts magnetic moments in ML CrI3 are 3.62 µB per chromium and -0.145 µB per iodine; both larger than previous DFT predictions. The large disparate moments together with the large spin-orbit coupling of CrI3's I-p orbital suggests a ligand superexchange-dominated magnetic anisotropy in ML CrI3, corroborating recent observations of magnons in its 2D limit. We also find ML CrI3 exhibits a substantial spin-phonon coupling of ∼ 3.32 cm −1 . Our work thus establishes many of ML CrI3's key properties, while also continuing to demonstrate the pivotal role DMC can assume in the study of magnetic and other 2D materials.

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A first-principles Quantum Monte Carlo study of two-dimensional (2D) GaSe

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Cited by 29 publications

References 110 publications

The intrinsic ferromagnetism of two-dimensional (2D) MnO$_2$ revisited: A many-body Quantum Monte Carlo and DFT+U study

The intrinsic ferromagnetism of two-dimensional (2D) MnO$_2$ revisited: A many-body Quantum Monte Carlo and DFT+U study

A quantum Monte Carlo study of systems with effective core potentials and node nonlinearities

A Combined First Principles Study of the Structural, Magnetic, and Phonon Properties of Monolayer CrI$_{3}$

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