Beyond Single-Reference Fixed-Node Approximation in Diffusion Monte Carlo Using Antisymmetrized Geminal Power Applied to Systems with Hundreds of Electrons.

Diffusion Monte Carlo (DMC) is an exact technique to project out the ground state (GS) of a Hamiltonian. Since the GS is always bosonic, in Fermionic systems, the projection needs to be carried out while imposing antisymmetric constraints, which is a nondeterministic polynomial hard problem. In practice, therefore, the application of DMC on electronic structure problems is made by employing the fixed-node (FN) approximation, consisting of performing DMC with the constraint of having a fixed, predefined nodal surface.

TurboGenius: Python suite for high-throughput calculations of ab initio quantum Monte Carlo methods.

TurboGenius is an open-source Python package designed to fully control ab initio quantum Monte Carlo (QMC) jobs using a Python script, which allows one to perform high-throughput calculations combined with TurboRVB [Nakano et al. J. Phys.

Evolutionary Algorithm Directed Synthesis of Mixed Anion Compounds LaF X (X=Br, I) and LaFI.

Mixed-anion compounds have attracted growing attentions, but their synthesis is challenging, making a rational search desirable. Here, we explored LaF -LaX (X=Cl, Br, I) system using ab initio structure searches based on evolutionary algorithms, and predicted LaF X and LaFX (X=Br, I), which are respectively isostructural with LaHBr and YH I, consisting of layered La-F blocks with single and double ordered honeycomb lattices, separated by van der Waals gaps. We successfully synthesized these compounds: LaF Br and LaFI crystallize in the predicted structure, while LaF I is similar to the predicted one but with different layer stacking.

Incidence and factor analysis for the heat-related illness on the Tokyo 2020 Olympic and Paralympic Games.

Introduction: Among the 43 venues of Tokyo 2020 Olympic Games (OG) and 33 venues of Paralympic Games (PG) were held, the heat island effect was highly expected to cause heat-related illnesses in the outdoor venues with maximum temperatures exceeding 35°C. However, the actual number of heat-related illness cases during the competition was lower than that was initially expected, and it was unclear under what conditions or environment-related heat illnesses occurred among athletes.

Object: To clarify the cause and factors contributing to the occurrence of heat-related illness among athletes participating in the Tokyo 2020 Olympic and Paralympic Games.

Toward Chemical Accuracy Using the Jastrow Correlated Antisymmetrized Geminal Power .

Herein, we report accurate atomization energy calculations for 55 molecules in the Gaussian-2 (G2) set using lattice regularized diffusion Monte Carlo (LRDMC). We compare the Jastrow-Slater determinant with a more flexible JsAGPs (Jastrow correlated antisymmetrized geminal power with singlet correlation) . AGPs is built from pairing functions, which explicitly include pairwise correlations among electrons, and hence, this is expected to be more efficient in recovering the correlation energy.

Topological Data Analysis for Revealing the Structural Origin of Density Anomalies in Silica Glass.

Topological data analysis (TDA) is a newly emerging and powerful tool for understanding the medium-range structure ordering of multiscale data. This study investigates the density anomalies observed during the cooling of liquid silica from a topological point of view using TDA. The density of liquid silica does not monotonically increase during cooling; it instead shows a maximum and minimum.

Shry: Application of Canonical Augmentation to the Atomic Substitution Problem.

A common approach for studying a solid solution or disordered system within a periodic framework is to create a supercell in which certain amounts of target elements are substituted with other elements. The key to generating supercells is determining how to eliminate symmetry-equivalent structures from many substitution patterns. Although the total number of substitutions is on the order of trillions, only symmetry-inequivalent atomic substitution patterns need to be identified, and their number is far smaller than the total.

Computational Design to Suppress Thermal Runaway of Li-Ion Batteries via Atomic Substitutions to Cathode Materials.

The cathode material of a lithium-ion battery is a key component that affects durability, capacity, and safety. Compared to the LiCoO cathode material (the reference standard for these properties), LiNiO can extract more Li at the same voltage and has therefore attracted considerable attention as a material that can be used to obtain higher capacity. As a trade-off, it undergoes pyrolysis relatively easily, leading to ignition and explosion hazards, which is a challenge associated with the application of this compound.

Diffusion Monte Carlo evaluation of disiloxane linearisation barrier.

The disiloxane molecule is a prime example of silicate compounds containing the Si-O-Si bridge. The molecule is of significant interest within the field of quantum chemistry, owing to the difficulty in theoretically predicting its properties. Herein, the linearisation barrier of disiloxane is investigated using a fixed-node diffusion Monte Carlo (FNDMC) approach, which is one of the most reliable methods in accounting for the electronic correlation.

Space-warp coordinate transformation for efficient ionic force calculations in quantum Monte Carlo.

Ab initio quantum Monte Carlo (QMC) methods are a state-of-the-art computational approach to obtaining highly accurate many-body wave functions. Although QMC methods are widely used in physics and chemistry to compute ground-state energies, calculation of atomic forces is still under technical/algorithmic development. Very recently, force evaluation has started to become of paramount importance for the generation of machine-learning force-field potentials.

A quantum annealing approach to ionic diffusion in solids.

We have developed a framework for using quantum annealing computation to evaluate a key quantity in ionic diffusion in solids, the correlation factor. Existing methods can only calculate the correlation factor analytically in the case of physically unrealistic models, making it difficult to relate microstructural information about diffusion path networks obtainable by current ab initio techniques to macroscopic quantities such as diffusion coefficients. We have mapped the problem into a quantum spin system described by the Ising Hamiltonian.

Pressure-Induced Collapse Transition in BaTiPnO (Pn = As, Sb) with an Unusual Pn-Pn Bond Elongation.

Making and breaking bonds in a solid-state compound greatly influences physical properties. A well-known playground for such bonding manipulation is the ThCrSi-type structure ATX, allowing a collapse transition where a X-X dimer forms by a chemical substitution or external stimuli. Here, we report a pressure-induced collapse transition in the structurally related BaTiPnO (Pn = As, Sb) at a transition pressure of ∼15 GPa.

General Correlated Geminal Ansatz for Electronic Structure Calculations: Exploiting Pfaffians in Place of Determinants.

We propose here a single Pfaffian correlated variational ansatz that dramatically improves the accuracy with respect to the single determinant one, while remaining at a similar computational cost. A much larger correlation energy is indeed determined by the most general two electron pairing function, including both singlet and triplet channels, combined with a many-body Jastrow factor, including all possible spin-spin, spin-density, and density-density terms. The main technical ingredient to exploit this accuracy is the use of the Pfaffian for antisymmetrizing a highly correlated pairing function, thus recovering the Fermi statistics for electrons with an affordable computational cost.

TurboRVB: A many-body toolkit for ab initio electronic simulations by quantum Monte Carlo.

TurboRVB is a computational package for ab initio Quantum Monte Carlo (QMC) simulations of both molecular and bulk electronic systems. The code implements two types of well established QMC algorithms: Variational Monte Carlo (VMC) and diffusion Monte Carlo in its robust and efficient lattice regularized variant. A key feature of the code is the possibility of using strongly correlated many-body wave functions (WFs), capable of describing several materials with very high accuracy, even when standard mean-field approaches [e.

All-Electron Quantum Monte Carlo with Jastrow Single Determinant Ansatz: Application to the Sodium Dimer.

In this work, we report potential energy surfaces (PESs) of the sodium dimer calculated by variational (VMC) and lattice-regularized diffusion Monte Carlo (LRDMC). The VMC calculation is accurate for determining the equilibrium distance and the qualitative shape of the experimental PES. Remarkably, after the application of the LRDMC projection to this single determinant ansatz, namely, the Jastrow Antisymmetrized Geminal Power (JAGP), chemical accuracy (∼1 kcal/mol) is reached in the binding energy, and the obtained equilibrium internuclear distance and harmonic vibrational frequency are in very good agreement with the experimental ones.

High-Pressure Synthesis of A NiO Ag Se (A=Sr, Ba) with a High-Spin Ni in Square-Planar Coordination.

Square-planar coordinate Ni ions in oxides are exclusively limited to a low-spin state (S=0) owing to extensive crystal field splitting. Layered oxychalcogenides A Ni O Ag Se (A=Sr, Ba) with the S=1 NiO square lattice are now reported. The structural analysis revealed that the Ni ion is under-bonded by a significant tensile strain from neighboring Ag Se layers, leading to the reduction in crystal field splitting.

Valence Band Engineering of Layered Bismuth Oxyhalides toward Stable Visible-Light Water Splitting: Madelung Site Potential Analysis.

A layered oxychloride BiNbOCl is a visible-light responsive catalyst for water splitting, with its remarkable stability ascribed to the highly dispersive O-2p orbitals in the valence band, the origin of which, however, remains unclear. Here, we systematically investigate four series of layered bismuth oxyhalides, BiOX (X = Cl, Br, I), BiNbOX (X = Cl, Br), BiGdOX (X = Cl, Br), and SrBiOX (X = Cl, Br, I), and found that Madelung site potentials of anions capture essential features of the valence band structures of these materials. The oxide anion in fluorite-like blocks (e.

[A Case of Retroperitoneal Mature Teratoma with Combined Resection of Left Kidney].

A 37-year-old woman with the complaint of stomachache was referred to our hospital because a retroperitoneal tumor was detected in an ultrasound study at another hospital. Magnetic resonance imaging showed a poorly enhanced 14 cm tumor in the left retroperitoneal space suggesting a cyst that contained fat and showed calcification. Abdominal dynamic computed tomography revealed left renal vein stenosis and left ovarian vein dilation caused by tumor compression of the renal vein.

Investigation into Structural Phase Transitions in Layered Titanium-Oxypnictides by a Computational Phonon Analysis.

We applied ab initio phonon analysis to layered titanium-oxypnictides, NaTiPnO (Pn = As and Sb), and found a clear contrast between the cases with lighter/heavier pnictogen in comparison with experiments. The result completely explains the experimental structure at low temperature, C2/m for Pn = As, within the conventional charge density wave, while there arise discrepancies when the pnictogen gets heavier. Our phonon calculation using the GGA-PBE functional predicts that a Cmce polymorph is more stable than the experimentally observed one (Cmcm) for Pn = Sb.

Hypervalent Bismuthides LaMBi (M = Ti, Zr, Hf) and Related Antimonides: Absence of Superconductivity.

We successfully synthesized the ternary bismuthides LaMBi (M = Ti, Zr, Hf). These compounds crystallize in the hexagonal HfSnCu-anti type structure (space group: P6/mcm) consisting of face-sharing MBi octahedral chains and hypervalent Bi linear chains, both separated by La atoms. Magnetic susceptibility and electrical resistivity measurements revealed that all of the compounds, including the solid solution LaTi(BiSb), exhibit a Pauli paramagnetic behavior without any trace of superconductivity down to 1.

Phonon dispersions and Fermi surfaces nesting explaining the variety of charge ordering in titanium-oxypnictides superconductors.

There has been a puzzle between experiments and theoretical predictions on the charge ordering of layered titanium-oxypnictides superconductors. Unconventional mechanisms to explain this discrepancy have been argued so far, even affecting the understanding of superconductivity on the compound. We provide a new theoretical prediction, by which the discrepancy itself is resolved without any complicated unconventional explanation.

[A clinical study of laryngotracheal separation in spinal muscular atrophy type I patients].

Artificial respiration by tracheostomy is necessary for long-term survival in spinal muscular atrophy (SMA) Type I patients. There are two types of tracheostomy: i )simple tracheostomy and ii) tracheostomy plus aspiration prevention surgery, including laryngotracheal separation. We experienced three cases of SMA type I patients that had good outcomes after undergoing laryngotracheal separation.

Successful treatment of early myoclonic encephalopathy using lidocaine and carbamazepine.

We report two female infants with early myoclonic encephalopathy (EME) whose intractable focal seizures were suppressed with lidocaine and carbamazepine (CBZ). Although EME is a form of early-onset epileptic encephalopathy characterised by myoclonus and focal seizures that are highly resistant to treatment, lidocaine and CBZ may prove effective in treating this disorder. Future studies should be performed in order to determine whether there are common specific mechanisms of seizure generation related to the sodium channel in these patients.