Ground State Parameters Research Articles

(Invited) How to Mitigate Excited State Polaron Formation in Transition Metal Oxide Photocatalysts

We measure how lattice versus electronic coupling in transition metal oxide photocatalysts can mitigate photoexcited polaron formation. Despite well-aligned energetics for photocatalysis, transition metal oxide materials have limited carrier mobilities due to the formation of polarons. The coupling of photoexcited charge carriers with phonons in the crystal lattice causes carrier localization and results in transport that relies on site-to-site hopping. Models that predict polaron formation are limited to ground-state predictions, which limits the exploration of new photocatalysts. Small polaron formation rates have been measured to be independent of defects, dopants, surface treatments, and other material tuning parameters. Our transient extreme ultraviolet (XUV) measurements show the first hints about how electronic correlations can be used to counter polaron formation for increased transport. For example, in CuFeO2, we add Cu layers between FeO6 octahedra, which increases photoexcited transport compared to α-Fe2O3. In ErFeO3, where Er frustrates FeO6 octahedra, coherent Fe-Fe charge hopping due to correlated electron interactions slows polaron formation. We frame our discussion in terms of the Hubbard-Holstein Hamiltonian, which we are slowly proving can be used to guide materials design rules for non-polaronic photocatalysts using only ground-state DFT parameters.

Opto‐Electronic Properties of Gap1‐xSbx Alloys for IR Applications

AbstractThe full potential linearized augmented plane wave (FP‐LAPW) method is used to compute structural, electronic, and optical properties of III‐V semiconductor ternary alloys GaP1‐xSbx (0≤x≤1) using first‐principle calculations within density functional theory. To calculate the ground state parameters of the structure, the energy exchange‐correlation Wu‐cohen generalized gradient approximation is employed in the wiek2k program. The Tran–Blaha‐modified Becke–Johnson (TB‐mBJ) pseudopotential is employed in addition to the Wu‐Cohen generalised gradient approximation to achieve a precise bandgap. After this, WC‐mBJ is used to examine optical properties such as real and imaginary parts of the dielectric constant, and energy loss. This study illustrates the nonlinear dependency on the various Sb compositions by examining the composition impacts on the bandgap, bulk modulus, and lattice constant. Using WC‐mBJ, the estimated band structures for alloys GaP0.75Sb0.25, GaP0.50Sb0.50, and GaP0.25Sb0.75 show direct energy bandgaps of 2.008 eV (617 nm), 1.482 eV (836 nm), and 1.055 eV (1174 nm), respectively. As a result, this material system has enormous potential for use in applications spanning the visible to infrared spectrum.

Optoelectronic and thermoelectric properties of novel double halide perovskites Na2AgAsX6 (X = Cl, Br) for efficient green solar cells

Inorganic lead-free double halide perovskites have emerged as promising materials in photovoltaic and renewable energy applications. This study investigates the optoelectronic and thermoelectric properties of novel inorganic lead-free double halide perovskite Na2AgAsX6 (X = Cl, Br) materials using accurate PBEsol and nKTB-mBJ schemes within the powerful full potential linear augmented plane wave (FP-LAPW) method. Structural ground state parameters were optimized, and the structural stability of these materials was assessed by evaluating their formation energy, phonon frequencies, and tolerance factor. Analysis of the electronic structure reveals that Na2AgAsX6 exhibit an indirect gap character, with energy values of 2.0 (for Cl) and 1.29 eV (for Br). Additionally, we computed various optical properties including dielectric functions (ε1, ε2), absorption coefficient (α), refractive index (n), extinction coefficient (k), and reflectivity (R), demonstrating a broad absorption spectrum spanning from visible to ultraviolet wavelengths. Furthermore, the investigation extends to determine the electronic transport properties—Seebeck coefficient (S), electrical conductivity (σ/τ), power factor (PF), thermal conductivity (κe/τ), and figure of merit (ZT) for Na2AgAsX6 (X = Cl, Br), using BoltzTraP code. These findings underscore the substantial potential of Na2AgAsX6 (X = Cl, Br) halide perovskites as efficient light absorption layers in the development of high-performance perovskite solar cells (PCSs) and also hold promise for future eco-friendly thermoelectric generator applications.

Re-analysis of the Gamow-Teller distributions for [formula omitted] nuclei, 24Mg, 28Si, and 32S

The Gamow-Teller (GT) strength distributions of sd-shell N=Z nuclei (24Mg, 28Si, and 32S) are investigated within the framework of proton–neutron quasi-particle random phase approximation (pn-QRPA) using a deformed basis. The nuclear properties of these special nuclei were investigated by the Relativistic Mean Field (RMF) model. The RMF framework with density-dependent interactions (DD-PC1 and DD-ME2) was employed to compute ground-state deformation parameters (β2) using potential energy curves. The β2 values computed from the RMF and the finite range droplet model (FRDM) were employed as a free parameter in the pn-QRPA calculation to investigate the resulting GT strength distributions. The present model-based analyses compare well with the observed data.

A computational study of the structural and thermal conduct of MgCrH3 and MgFeH3 perovskite-type hydrides: FP-LAPW and BoltzTraP insight

The structural and thermal conduct of MgCrH3 and MgFeH3 perovskite have been investigated using the full-potential linearized augmented plane wave (FPLAPW) method and the BoltzTraP package, implemented in the Wien2k code. The calculations involved fitting the Murnaghan equation of state to the calculated total energy and atomic volume. The present analysis includes key groundstate parameters, such as the lattice parameter and its pressure derivative. Where the electrical conductivity of MgTMH3 (TM=Cr and Fe), the thermal conductivity, merit factor, and power factor were discussed in the range of 300-900 K. The obtained outcomes exhibit interesting results to make these compounds as promising materials for thermoelectrical applications.

DFT calculations of optoelectronic and thermoelectric properties of K2NaTlX6 (X = Cl, Br, I) halide double perovskites for energy harvesting applications

The DFT approach was employed to investigate the mechanical, optical and thermoelectric properties of double perovskites (DPs) compounds K2NaTlX6 (X = Cl, Br, I). PBEsol-GGA approximation along with birch-Murnaghan equation is used to calculate the lattice constant, other structural and ground state parameters. The structural, thermodynamic and mechanical stability of these compounds was demonstrated by computing tolerance factor, formation energy and Born criteria. Poisson and Pugh ratio are analyzed to describe the brittle or ductile nature of these studied double perovskites compounds. The anion Cl, Br and I-based double perovskites exhibited direct bandgap as determined from band structure calculations. The study further examined the optical absorption and dielectric constant of the compounds across the energy range 0–10 eV confirming their ability to absorb light in the infrared to visible spectrum. Furthermore, the suitability of the studied double perovskites for thermoelectric applications was assessed using BoltzTraP coding. The Seebeck coefficient, electric conductivity and figure of merit were analyzed, suggesting that these compounds hold promise as viable candidates for thermoelectric applications.

Correlating Metal Redox Potentials to Co(III)K(I) Catalyst Performances in Carbon Dioxide and Propene Oxide Ring Opening Copolymerization.

Carbon dioxide copolymerization is a front-runner CO2 utilization strategy but its viability depends on improving the catalysis. So far, catalyst structure-performance correlations have not been straightforward, limiting the ability to predict how to improve both catalytic activity and selectivity. Here, a simple measure of a catalyst ground-state parameter, metal reduction potential, directly correlates with both polymerization activity and selectivity. It is applied to compare performances of 6 new heterodinuclear Co(III)K(I) catalysts for propene oxide (PO)/CO2 ring opening copolymerization (ROCOP) producing poly(propene carbonate) (PPC). The best catalyst shows an excellent turnover frequency of 389 h-1 and high PPC selectivity of >99 % (50 °C, 20 bar, 0.025 mol% catalyst). As demonstration of its utility, neither DFT calculations nor ligand Hammett parameter analyses are viable predictors. It is proposed that the cobalt redox potential informs upon the active site electron density with a more electron rich cobalt centre showing better performances. The method may be widely applicable and is recommended to guide future catalyst discovery for other (co)polymerizations and carbon dioxide utilizations.

Thermodynamic and thermoelectric properties of FeCrTiZ (Z = Si, Ge) quaternary Heusler compounds

The objective of this work is to find the possible applications of the compounds as thermoelectric materials or alternate energy materials. In this regard, FeCrTiZ (Z = Si, Ge) quaternary Heusler compounds have been analyzed via investigating their stable structure and other physical properties by using comprehensive density functional theory executed in the WIEN2k package. The optimized lattice constants and other ground state parameters are found to be concurrent with the existing data. The spin-embraced electronic properties lead to the half-metallic character of the compounds on account of different behavior of the two spins. The obtained total magnetic moment ideally follows the Pauling-Slater rule and is also congruent to the available data. Furthermore, to study the lattice vibrational properties, the dependence of unit cell volume, bulk modulus, Debye temperature, and Gruneisen constant has been estimated within a certain temperature and pressure range by employing a Debye model of quasi-harmonic approximation. The thermoelectric parameters have also been estimated by employing the BoltzTrap code which gives significant values of the figure of merit for both compounds.

On some ground state properties of extended t-J-U model induced by Next-Nearest-Neighbor (NNN) pair hopping interaction

Considering an 8-site tilted square cluster, effect of NNN pair hopping interaction Y' on some ground state parameters like ground state energy E0, hole-hole correlation Phh, and spin–spin correlation C(l) of high-Tc superconductors (HTSC) have been examined at a hole doping concentration < h> = 0.25. The system has been described by two-dimensional (2D) extended t-J-U Hamiltonian. Calculations are based on Lanczos method. Slight decrease in E0 is observed with Y'. Phh between NNN sites increases with Y'. A short range antiferromagnetic (AF) order emerges when Y' is greater than one third of NN pair hopping interaction (Y). Correlated hopping interaction renormalizes Y'.

High resolution spectroscopy of asymmetric top molecules in nonsinglet electronic states: the ν3 fundamental of chlorine dioxide (16O35Cl16O) free radical in the X2B1 electronic ground state.

Highly resolved spectra of the 16O35Cl16O isotopologue of chlorine dioxide were recorded with a Bruker IFS 125HR Fourier transform infrared spectrometer in the region of the ν3 band. The analysis was made in the frame of the spin-rotational effective Hamiltonian (in A-reduction and Ir-representation) taking into account spin-rotational coupling operators up to the sixth order and the corresponding reduction of the Hamiltonian. The mathematical description of the ro-vibrational spectra was implemented to the specially created computer program ROVDES. Under the present experimental conditions, we were able to assign more than 5200 spin-rotational transitions to the ν3 band. This number is 2.4 times higher compared to the previous studies available from the literature. The vibrational ground state parameters were improved, and the 2220 upper spin-rotation-vibration energy levels were determined and used as initial data in the inverse spectroscopic problem with the derived effective spin-rotational Hamiltonian. A total of 37 fitted parameters were determined (22 rotational and centrifugal parameters and 15 parameters of spin-rotation coupling). The appearance of strong Coriolis resonance interactions between the (001) and (100) vibrational states in the sets of (001)[N,Ka = 9], (001)[N,Ka = 17], (001)[N,Ka = 18] and (001)[N,Ka = 19] spin-rotation-vibration levels was experimentally observed for the first time and explained. The drms = 1.4 × 10-4 cm-1 reproduction of the initial "experimental" upper ro-vibrational energy values was achieved which is considerably better compared to the use of parameters from a previous study ([J. Ortigoso et al., J. Mol. Spectrosc., 1992, 155, 25-43]).

Structural, Electronic and Optical Properties of Titanium Based Fluoro-Perovskites MTiF3 (M = Rb and Cs) via Density Functional Theory Computation.

This study reports the theoretical investigations on the structural, electronic, and optical properties of titanium-based fluoro-perovskites MTiF3 (M = Cs and Rb) using density functional theory. The impact of on-site Coulomb interactions is considered, and calculations are performed in generalized gradient approximation with the Hubbard U term (GGA + U). The ground state parameters, such as lattice constants, bulk modulus, and pressure derivatives of bulk modulus, were found. These compounds are found stable in cubic perovskite structures having lattice constants of 4.30 and 4.38 Å for RbTiF3 and CsTiF3, respectively. Analysis of elastic properties shows that both of the compounds are ductile in nature. According to the band structure profile, the examined compounds have a half-metallic character, exhibiting conducting behavior in the spin-up configuration and nonconducting behavior in the spin-down configuration. The ferromagnetic nature is conformed from the study of its magnetic moments. The optical behaviors such as reflectivity, absorption, refraction, and conductivity of the cubic phase of MTiF3 (M = Rb and Cs) are studied in the energy range of 0-40 eV.

Optical Conductivity as a Probe of the Interaction-Driven Metal in Rhombohedral Trilayer Graphene

Study of the strongly correlated states in van der Waals heterostructures is one of the central topics in modern condensed matter physics. Among these, the rhombohedral trilayer graphene (RTG) occupies a prominent place since it hosts a variety of interaction-driven phases, with the metallic ones yielding exotic superconducting orders upon doping. Motivated by these experimental findings, we show within the framework of the low-energy Dirac theory that the optical conductivity can distinguish different candidates for a paramagnetic metallic ground state in this system. In particular, this observable shows a single peak in the fully gapped valence-bond state. On the other hand, the bond-current state features two pronounced peaks in the optical conductivity as the probing frequency increases. Finally, the rotational symmetry breaking charge-density wave exhibits a minimal conductivity with the value independent of the amplitude of the order parameter, which corresponds precisely to the splitting of the two cubic nodal points at the two valleys into two triplets of the band touching points featuring linearly dispersing quasiparticles. These features represent the smoking gun signatures of different candidate order parameters for the paramagnetic metallic ground state, which should motivate further experimental studies of the RTG.

Chemical design of boron-nitride nanotubes, nanotubes by Gaussian 5.0 version

In this study, nano tube modular is utilized to create a graphene nano-ribbon structure with n=m=4 and a tube length of 1 nm. For the display system, export the structure to the Gaussian 5.0 version. The input data is then exported to Gaussian 09, which is used to calculate geometrical and electrical parameters, as well as adsorption energy. The ground state parameters were computed using the DFT approach, which was dependent on electron density. Higher Occupied Molecular Orbitals (HOMO) and Lower Unoccupied Molecular Orbitals (LUMO) are produced by molecular orbital energy, and the energy gap.

First-principles calculations on novel Co-based Equiatomic Quaternary Heusler Alloys for Spintronics

The structural, mechanical, electronic, and magnetic properties of the new series of Co-based Equiatomic Quaternary Heusler Alloys (EQHAs) XX'YZ (X = Co; X' = Zr, Ru; Y = Ti, V; Z = Sn, Al, Ga, Si, Ge) have been calculated using first-principles calculations. The Full Potential-Linearized Augmented Plane Wave (FP-LAPW) approach was used in association with Density Functional Theory (DFT). We treated the exchange-correlation (XC) energy functional using a Generalized Gradient Approximation (GGA) in the Perdew-Burke-Ernzerhof (PBE) scheme. We included the TB-mBJ potential (GGA-mBJ) and the Hubbard correction (GGA + U) to improve the precision of the band gap values. Spin-orbit coupling (GGA-SOC) calculations are required due to the existence of heavier elements such as Zr and Ru. We have included the GGA-SOC calculations to estimate the total and partial magnetic moment and their impact on the electronic structure of Co-based EQHAs. The ground state parameters of proposed Co-based EQHAs were determined, including the lattice parameter, total energy, bulk modulus, and its derivative. The electronic structure of these materials revealed the presence of half-metallic ferromagnetism and spin-gapless semiconductor behavior. In addition, the origin of the band gap in spin channels was also investigated. In addition, we employed the mean-field approximation (MFA) method based on the Heisenberg model to determine the Curie temperature (TC). This theoretical analysis adds a new level of sophistication to the application of Co-based EQHAs in spintronic applications.

Detailed analysis of excited-state systematics in a lattice QCD calculation of gA

Excited state contamination remains one of the most challenging sources of systematic uncertainty to control in lattice QCD calculations of nucleon matrix elements and form factors: early time separations are contaminated by excited states and late times suffer from an exponentially bad signal-to-noise problem. High-statistics calculations at large time separations $\gtrsim1$ fm are commonly used to combat these issues. In this work, focusing on $g_A$, we explore the alternative strategy of utilizing a large number of relatively low-statistics calculations at short to medium time separations (0.2--1 fm), combined with a multi-state analysis. On an ensemble with a pion mass of approximately 310 MeV and a lattice spacing of approximately 0.09 fm, we find this provides a more robust and economical method of quantifying and controlling the excited state systematic uncertainty. A quantitative separation of various types of excited states enables the identification of the transition matrix elements as the dominant contamination. The excited state contamination of the Feynman-Hellmann correlation function is found to reduce to the 1% level at approximately 1 fm while for the more standard three-point functions, this does not occur until after 2 fm. Critical to our findings is the use of a global minimization, rather than fixing the spectrum from the two-point functions and using them as input to the three-point analysis. We find that the ground state parameters determined in such a global analysis are stable against variations in the excited state model, the number of excited states, and the truncation of early-time or late-time numerical data.

Crystal density of CaS under pressure up to 40 GPa

Based on the experimental ground state parameters reported in the literature (Luo et al., Phys. Rev. B 50 (1994)16232-16237); in the present work we reproduce the variation in the volume with the pressure up to 40 GPa for calcium sulfide (CaS) compound, which criticized in cubic rock-salt structure. We used two different models of equation of state (EOS); the fist is the model of Vinet, while the second one is the EOS Murnaghan’s model. We studied also the effect of the pressure on the crystal density. We established some analytical models relating the volume with the pressure, as well as the crystal density with the pressure.Finally, we predicted the melting point, the Debye temperature and the sound velocity of CaS material, which are 1202.2 K, 423.7 K, and 4049.5 m/s, respectively.  Â

High–resolution spectroscopy of C2H3D: Line positions and energy structure of the strongly interacting [formula omitted] and [formula omitted] bands

High resolution infrared spectra of C2H3D were recorded in the region of 550–1950 cm−1 with a Bruker IFS125 HR Fourier transform infrared spectrometers and rotational structures of the five lowest strongly interacting ν10, ν7,ν8,ν4 and ν6 bands were analyzed. The number of about 28000 transitions (4200/6800/5600/5000/6400 for the bands ν10,ν7,ν8,ν4 and ν6) with Jmax = 40 and Kamax = 20 were assigned to these five bands. The weighted fit of 3990 upper energy values obtained from the experimentally recorded transitions was made with a Hamiltonian which takes into account resonance interactions between all studied bands as well as with the sixth ν3 band which was considered in this case as a “dark” one. As the result of analysis, a set of 279 fitted parameters was obtained which reproduces the initial 3990 upper “experimental” ro–vibrational energy values with the drms=1.7×10-4 cm−1; the initial nonsaturated, unblended and not very weak of 28000 assigned transitions are reproduced with the drms=2.2×10-4 cm−1. Ground state parameters of the C2H3D molecule were improved as well.

DFT Study of ScP and AlP in B1, B2, and B3 Phases at Ambient Pressure

Structural, electronic, elastic, and dynamic characteristics of scandium phosphide and aluminium phosphide compounds are studied theoretically. The study has been performed for rock salt (B1), CsCl (B2), and zinc blend (B3). We use the density functional theory, which is based on the plane wave basis and the pseudopotential approach, as implemented in the Quantum Espresso Software package. ScP and AlP exhibits metallic behavior in the B1 and B2 phases. The B3 phase of ScP displays a semiconductor characteristic with a broad and straight band gap at X of (1.617). In AlP, the B3 phase exhibits semiconductor characteristics with an indirect band gap at Г-X of (1.60). Both compounds ScP and AlP on B1, B2, and B3 structures report computed ground state parameters. The zinc blend phase is the most stable of the three phases, according to the findings. Our computed results are in good agreement with earlier investigations. The work presented in this article is related to sustainable development goals (SDGs) to transform our world regarding industry, innovation, and infrastructure.

Revised assignments of the v4=1 vibrational level of CH35Cl3: The ν4 and ν4-ν3 rovibrational bands with remarkable clustering effects

The v4 = 1 fundamental vibration of chloroform (C-H bending vibration, E symmetry) has been reinvestigated at high-resolution. For this purpose, FTIR spectra recorded in the regions of the ν4 (1220 cm−1) and ν4 − ν3 (853 cm−1) bands were employed. Spectra were recorded at the Synchrotron Soleil, using a monoisotopic CH35Cl3 sample. More than 6900 transitions were assigned, among which more than 4200 in the difference band. Assignments span the 0 ≤ J ≤ 100 and − 75 ≤ K′′ΔK ≤ 75 values, despite the systematic overlaps of transitions, observed over a wide range of the spectrum. These overlaps, giving rise to remarkable clustering effects, are characteristic of both the fundamental ν4 and the difference ν4-ν3 bands. They are also, sometimes, source of misassignments, especially when the systematic use of the lower state combination differences as a checking is not possible. In this regard, we have to notice here that the indirect assignment checking through fundamental and difference transitions sharing a common upper level allowed us to systematically correct and extend the K-assignments of the rRK(J) transitions in the ν4 band.In the least-squares fit, the ground state parameters were fixed to the most recent experimental values. The parameters of the v3 = 1 level could be refined and improved with respect to previous determination, thanks to about 800 IR data collected from a FTIR spectrum of the ν3 band, together with more than 1300 MMW data in the v3 = 1 level (22 ≤ J ≤ 98 and 0 ≤ K ≤ 79).The theoretical model used for the v4 = 1 fundamental vibration is that of an isolated vibrational level, and ten molecular parameters were refined; the global standard deviation of the fit was of 0.160 × 10−3 cm−1, which is of the order of the accuracy of the experimental data.

Structural evolution and shape transition in even-even Hf-isotopes within the relativistic mean-field approach

In this theoretical study, we calculate the ground state parameters like binding energy, charge radii, neutron skin-thickness, chemical potentials, quadrupole deformation parameter, neutron separation energy, and single-particle energy for Hf isotopes of mass 170 ⩽ A ⩽ 220. The potential energy surface in parallel with the Fermi energy as a function of the quadrupole deformation parameter is estimated to determine the ground state configuration. The Relativistic Hartree-Bogoliubov approach with density-dependent DD-ME2 and the relativistic mean-field formalism with the popular NL3 and NL3⁎ parameter sets are used for the present analysis. The study involves a constant gap BCS approach within NL3, & NL3⁎ and Bogoliubov transformation within DD-ME2 parameter sets to examine the effect of pairing correlations. The calculated bulk quantities are reasonably good agreement with available experimental data, the finite range droplet model predictions, and the Weizsäcker-Skyrme mass formula. We find the signature of shell/sub-shell closure at N = 126 for all the parameter sets, which indicates the stability of 198Hf in the neutron drip-line region of the Hf-isotopes.