Set Of Crystal Field Parameters Research Articles

Theoretical Determination of the Electronic Structures and Energy-Level Splitting for Pr3+-Doped Y2SiO5 Crystals.

Trivalent praseodymium (Pr3+)-doped yttrium silicate (Y2SiO5) crystals have been widely used in various phosphors owing to their excellent luminescence characteristics. Although a series of studies have been carried out on its application prospects, the electronic structures and energy-transfer mechanisms of Pr3+-doped Y2SiO5 (Y2SiO5:Pr) remain an exploratory topic. Herein, the crystal structure analysis by the particle swarm optimization structure search method is used to study the structural evolution of Y2SiO5:Pr. Two novel structures with local [PrO7]-11 and [PrO6]-9 [Y2SiO5:Pr (I) and Y2SiO5:Pr (II)] are successfully identified. The impurity Pr3+ ions occupy the Y3+ sites and successfully integrate into the Y2SiO5 host crystal with a Pr3+ concentration of 6.25%. The calculated electronic band structures show that the doping of Pr3+ induces a reduction in band gaps for the host Y2SiO5 crystal. The conduction bands near the Fermi level are completely composed of f states. For the atomic energies of Pr3+ in Y2SiO5, the Stark levels and transitions are properly simulated based on a new set of crystal field parameters (CFPs) at the C1 site symmetry. A satisfactory r.m.s. dev. of 15.57 cm-1 with 9 free ion parameters (plus 27 fixed CFPs as obtained from ab initio calculation) fitted to the 33 observed levels is obtained for the first time. The plentiful energy-level transition lines, from the visible light to the near-infrared region, are deciphered for Pr3+ in Y2SiO5. Blue 3P0 → 3H4 at 465 nm is calculated to be a strong emission line, and it might be an ideal channel for laser actions. These results could not only provide important insights into the rare-earth-doped crystals but also lay the foundation for future research studies of designing the new laser materials.

Laser spectroscopy and crystal field analysis of energy level structure of Tm3+ ions in SrY2O4 crystal

Site-selective laser spectroscopy study of the multi-site SrY2O4:Tm3+ crystal (0.05 at.%) show that two types of impurity centers of Tm3+ ions are predominantly formed. The Stark sublevel patterns of the 3H6, 3H5, 3F4, 3H4, 3F3, and 1G4 multiplets have been determined. Calculations of the energy level structure for Tm3+ ions at Y1 and Y2 lattice sites have been carried out in the framework of the crystal-field theory. The obtained calculation results agree with the measured energy spectra, supporting an assignment of spectra to Tm3+ ions at Y1 and Y2 lattice sites. To verify the correctness of the performed calculations, the field dependencies of the magnetization along the crystallographic a, b and c axes and the temperature dependence of the magnetization in the magnetic field applied along the c-axis of the SrY2O4:Tm3+ (0.5 at.%) crystal were measured. The set of crystal-field parameters obtained in this work made it possible to fully describe the measured magnetization dependences.

Eu3+ ions as a crystal-field probe for low-symmetry sites in doped phosphors - a case study: Eu3+ at triclinic sites in Li6RE(BO3)3 (RE = Y, Gd), YBO3 and ZnO and at trigonal sites in YAl3(BO3)4.

We present crystal-field (CF) calculations of energy levels (Ei) of Eu3+ ions doped in various hosts aimed at exploring the low-symmetry properties of CF parameters (CFPs) and reliability of CFP modelling with decreasing site symmetry. The hosts studied are: Li6Y(BO3)3, Li6Gd(BO3)3, YBO3, and ZnO with Eu3+ at triclinic sites; YAl3(BO3)4 with Eu3+ ions at trigonal D3 symmetry. Two independent CFP modelling approaches utilizing the hosts' structural data are employed: the exchange charge model (ECM) and the superposition model (SPM). We adopt the Eu3+ actual site symmetry and not the approximated one. The Ei values calculated using CFPs modelled by the ECM and SPM mutually agree with the observed ones. For triclinic symmetry, the ECM/CFPs and SPM/CFPs were numerically distinct, yet turned out to be physically equivalent yielding identical rotational invariants, Sk (k = 2, 4, 6) and Ei. For trigonal symmetry, both CFP sets agree numerically, thus Sk and Ei are identical. This disparity poses a dilemma, since the modified crystallographic axis system was used in both approaches. The standardization of the triclinic CFPs using the 3DD package was performed to solve this dilemma. It has enabled discussing standardization aspects in experimental and computed CFP sets and elucidating intricate low-symmetry aspects inherent in CFP sets. Understanding of low-symmetry aspects in CF studies may bring about a better interpretation of the spectroscopic and magnetic properties of rare-earth ion doped host crystals. Thus, our study could provide more deep insights into the importance of clear definitions of axis systems and adequate treatment of actual site symmetry in the modelling of CFPs for low-symmetry cases which is essential for technological applications and engineering of rare-earth activated phosphor materials.

Analysis of crystal-field effects on the energy levels of Mn4+ ions doped in different photoluminescent host lattices, exhibiting lowering of site symmetry: Exchange charge and superposition model calculations, for potential applications

Herein, we presented a comparative analysis of crystal-field (CF) effects on the energy levels of Mn4+ ions doped in the various host lattices exhibiting site symmetry from: triclinic: Y2MgTiO6, La2MgTiO6, Ca2YTaO6, Ca2YSbO6; trigonal: Ba2LaSbO6, LaTiSbO6; tetragonal: Ba2GdTaO6; to octahedral: Li2MgTiO4, Ba2GdSbO6, Ba2YSbO6. For modelling CF parameters (CFPs), we employed exchange charge model (ECM) using one model parameter (G), and superposition model (SPM) using four model parameters. A modified crystallographic axis system (CAS*) was adopted in ECM and SPM calculations for low symmetry hosts. The modelled CFPs served as input for crystal-field analysis/microscopic spin-Hamiltonian program to calculate the Mn4+ energy levels and match them with photoluminescence spectra of Mn4+-doped crystals. The 2nd-rank ECM/CFPs vary with G depending on distortions of the metal (M)-ligand (L) MLn polyhedron. The 4th-rank ECM/CFPs depend predominantly on the exchange charge effects. The ECM yields seemingly a better agreement between the observed and calculated energies than the SPM one. The disparity between the CFP sets calculated using SPM and ECM approaches in CAS*, while yielding same CFP strength, poses dilemmas. To solve these dilemmas, we employed the triclinic standardization of CFP sets, thus uncovering intricate low symmetry aspects inherent in ECM/CFPs, hitherto not realized. This method proved very useful for meaningful analysis and interpretation of CFP sets. Our CFP modelling illustrates importance of well-defined axis systems and adequate treatment of the actual triclinic (and monoclinic) site symmetry of dopant ions, instead of octahedral symmetry (usually adopted by experimentalists), in modelling of CFPs for triclinic symmetry cases. The relations between the Racah parameters, B and C, and 2Eg → 4A2g peak emission energy of Mn4+ ions are extended and suitably modified for triclinic symmetry. These modifications may be significant in engineering the local CF environment by suitably choosing the host crystals and dopant ions to improve the luminescence properties of phosphors for practical applications. The influence of dopant metal ions on the local structure and thus spectroscopic properties of doped crystals was also explored.

Unraveling the local structure and luminescence evolution in Nd3+-doped LiYF4: a new theoretical approach.

Neodymium ion (Nd3+)-doped yttrium lithium fluoride (LiYF4, YLF) laser crystals have shown significant prospects as excellent laser materials in many kinds of solid-state laser systems. However, the origins of the detailed information of their local structure and luminescence evolution are still poorly understood. Herein, we use an unbiased CALYPSO structure searching technique and density functional theory to study the local structure of Nd3+-doped YLF. Our results reveal a new stable phase with the P4[combining macron] (No. 81) space group for Nd3+-doped YLF, indicating that the host Y3+ ion site was naturally occupied by the Nd3+ ion impurity. On the basis of our newly developed WEPMD method, we adopt a specific type of orthogonal correlation crystal field to obtain a new set of crystal-field parameters as well as 182 complete Stark energy levels. Many absorption and emission lines for Nd3+-doped YLF are calculated and discussed based on Judd-Ofelt theory, and our results indicate that some of the observed absorption and emission lines are perfectly reproduced by our theoretical calculations. Additionally, we predict several promising transition lines in the visible and near-infrared spectral regions, including the electronic dipole emission lines 4F5/2 → 4I9/2 at 808 nm and 2H9/2 → 4I9/2 at 799 nm, as well as the magnetic dipole emission lines 4F3/2(27) → 4I11/2(6) at 1047 nm and 4F3/2(27) → 4I11/2(8) at 1052 nm. These transition channels indicate that Nd3+-doped YLF laser crystals have greatly promising laser actions for serving as a solid-state laser material.

High-resolution spectroscopy of rare-earth ferroborates with a huntite structure

A review of spectroscopic study results of rare-earth (RE) ferroborate crystals RFe3(BO3)4, R = Pr–Er, Y. High-resolution spectroscopy is used to study the structural and magnetic phase transitions, spin-phonon and electron-phonon interactions. Physically justified sets of crystal-field parameters are determined, and a number of RE ferroborate properties are simulated.

Crystal field and hyperfine structure of Er3+167 in YPO4 :Er single crystals: High-resolution optical and EPR spectroscopy

We report on a high-resolution optical and magneto-optical spectroscopy, luminescence, and electron paramagnetic resonance (EPR) studies of yttrium orthophosphate single crystals doped with erbium, which are promising telecom-wavelength materials for applications in quantum electronics and quantum information processing. An observation of the hyperfine structure in optical spectra of $^{167}\mathrm{Er}$ isotope in ${\mathrm{Er}:\mathrm{YPO}}_{4}$ is presented. Energies and symmetries of 40 crystal-field levels of ${\mathrm{Er}}^{3+}$ in ${\mathrm{Er}:\mathrm{YPO}}_{4}$ and $g$ factors of some of them were determined and successfully modeled on the basis of crystal-field calculations. The obtained set of crystal-field parameters was used in modeling the hyperfine structure observed in the optical and EPR spectra of ${\mathrm{Er}:\mathrm{YPO}}_{4}$ single crystals.

The crystal-field states and the magnetism in the Kondo-lattice antiferromagnet CeRh[formula omitted]Si[formula omitted

We have theoretically analysed temperature dependence of the specific heat at temperatures below 50 K of a Kondo-lattice antiferromagnet CeRh2Si2. We have reproduced experimentally-observed λ-type peak at the magnetic-ordering temperature TN of 36.5 K as originating from the splitting of the Kramers-doublet ground state of the Ce3+ ion. We have derived a set of crystal-field parameters, which, apart of the reproduction of crystal-field excitations of 30 and 52 meV, of the temperature dependence of the specific heat and of the paramagnetic susceptibility, reproduces a value of the magnetic moment, of 1.60 μB. Our results for the temperature dependence of the specific heat and of the entropy are physically adequate and substantially improved compared to theoretical descriptions reported in a recent publication in Nature Comm. (7 (2016) 11029).A good reproduction of the physical magnetic and electronic properties indicates that 99±1% of Ce ions are in the 4f1 configuration. A large value of the entropy removed in the magnetic transition, very close to Rln2, indicates that the hybridization effects and a broadening of crystal-field states in CeRh2Si2 are very small. The Quantum Atomistic Solid-State Theory (QUASST) approach can be used for the theoretical description of magnetic and electronic properties of other Ce, rare-earth and actinides compounds.

Electronic Structure and Magnetic Anisotropy in Lanthanoid Single-Ion Magnets with C3 Symmetry: The Ln(trenovan) Series.

We report the syntheses and the magnetic characterization of a new series of lanthanide complexes, in which the Ce, Nd, Gd, Dy, Er, and Yb derivatives show single-molecule magnet behavior. These complexes, named Ln(trenovan), where H3trenovan is tris(((3-methoxysalicylidene)amino)ethyl)amine, exhibit trigonal symmetry and the Ln(III) ion is heptacoordinated. Their molecular structure is then very similar to that of the previously reported Ln(trensal) series, where H3trensal is 2,2',2″-tris(salicylideneimino)triethylamine. This prompted us to use the spectroscopic and magnetic properties of the Ln(trensal) family (Ln = Nd, Tb, Dy, Ho, Er, and Tm) to obtain a set of crystal-field parameters to be used as starting point to determine the electronic structures and magnetic anisotropy of the analogous Ln(trenovan) complexes using the CONDON computational package. The obtained results were then used to discuss the electron paramagnetic resonance (EPR) and ac susceptibility results. As a whole, the obtained results indicate for this type of complexes single-molecule magnet behavior is not related to the presence of an anisotropy barrier, due to a charge distribution of the ligand around the lanthanoid, which results in highly mixed ground states in terms of MJ composition of the states. The crucial parameter in determining the slow relaxation of the magnetization is then rather the number of unpaired electrons (only Kramers ions showing in-field slow relaxation) than the shape of the charge distribution for different Ln(III).

Crystal-field parameters of the rare-earth pyrochloresR2Ti2O7(R=Tb, Dy, and Ho)

In this work we present inelastic neutron scattering experiments which probe the single ion ground states of the rare earth pyrochlores $R_2$Ti$_2$O$_7$ ($R$ = Tb, Dy, Ho). Dy$_2$Ti$_2$O$_7$ and Ho$_2$Ti$_2$O$_7$ are dipolar spin ices, now often described as hosts of emergent magnetic monopole excitations; the low temperature state of Tb$_2$Ti$_2$O$_7$ has features of both spin liquids and spin glasses, and strong magnetoelastic coupling. We measured the crystal field excitations of all three compounds and obtained a unified set of crystal field parameters. Additional measurements of a single crystal of Tb$_2$Ti$_2$O$_7$ clarified the assignment of the crystal field levels in this material and also revealed a new example of a bound state between a crystal field level and an optical phonon mode.

4fexcitations in Ce Kondo lattices studied by resonant inelastic x-ray scattering

The potential of resonant inelastic soft x-ray scattering to measure $4f$ crystal electric-field excitation spectra in Ce Kondo lattices has been examined. Spectra have been obtained for several Ce systems and show a well-defined structure determined by crystal-field, spin-orbit, and charge-transfer excitations only. The spectral shapes of the excitation spectra can be well understood in the framework of atomic multiplet calculations. For ${\mathrm{CeCu}}_{2}{\mathrm{Si}}_{2}$ we found notable disagreement between the inelastic x-ray-scattering spectra and theoretical calculations when using the crystal-field scheme proposed from inelastic neutron scattering. Modified sets of crystal-field parameters yield better agreement. Our results also show that, with the very recent improvements of soft x-ray spectrometers in resolution to below 30 meV at the Ce ${M}_{4,5}$ edges, resonant inelastic x-ray scattering could be an ideal tool to determine the crystal-field scheme in Ce Kondo lattices and other rare-earth compounds.

Standardization of crystal field parameters for rare-earth (RE3+) ions at monoclinic sites in selected laser crystals

Survey of spectroscopic studies of trivalent rare-earth (RE3+) ions at orthorhombic or monoclinic sites in various crystals, which are important in view of promising technological applications, has revealed a number of crystal field (CF) parameter (CFP) sets belonging to different ranges in the CF parameter space. This indicates that the major properties of orthorhombic and monoclinic CF Hamiltonians have not been fully realized in literature. This includes the existence of alternative, i.e. physically equivalent, CF parameter (CFP) sets and incorrectness of comparison of such alternative yet disparate CFP sets, which due to their intrinsic features cannot be directly compared. Proper methodology for dealing with such CFP sets has been outlined earlier. In this paper we consider implications of these properties for interpretation of (i) spectroscopic data for rare-earth ions obtained from several experimental techniques and (ii) the axis systems in which the fitted CFPs are supposedly expressed. Since these aspects are not realized by many researchers, incorrect conclusions concerning, e.g. the strength of CF and structural implications, have often been drawn. The standardization approach is employed for meaningful comparative analysis of the CFP sets for RE3+ ions at monoclinic sites in selected laser crystals. The following ion-host systems are studied: Nd3+: LuAlO3, Nd3+: BaY2F8, Eu3+: Gd2O3, Eu3+, Pr3+, Tb3+, Ho3+, Tm3+, Nd3+, Sm3+, Dy3+, Er3+: Y2O3, Er3+: Er2O3, Pr3+, Sm3+, Gd3+, Er3+: LaF3, Er3+: YAlO3. A representative sample of CFP sets is analyzed, standardized, and presented in a unified way. The alternative CFP sets provided here may be utilized in the multiple correlated fitting technique to improve reliability of final fitted CFPs. The present approach may facilitate future spectroscopic determination of CFPs as well as increase reliability of fitted and theoretical CFPs for fN (RE3+) ions at lower symmetry sites.

Calculations of the magnetic properties of R2M14B intermetallic compounds (R=rare earth, M=Fe, Co)

The hard magnetic properties of “R–M–B” (R=rare earth, M=mainly Fe) magnets derive from the specific intrinsic magnetic properties encountered in Fe-rich R2M14B compounds. Exchange interactions are dominated by the 3d elements, Fe and Co, and may be modeled at the macroscopic scale with good accuracy. Based on classical formulae that relate the anisotropy coefficients to the crystalline electric field parameters and exchange interactions, a simple numerical approach is used to derive the temperature dependence of anisotropy in various R2Fe14B compounds (R=Pr, Nd, Dy). Remarkably, a unique set of crystal field parameters give fair agreement with the experimentally measured properties of all compounds. This implies reciprocally that the properties of compounds that incorporate a mixture of different rare-earth elements may be predicted accurately. This is of special interest for material optimization that often involves the partial replacement of Nd with another R element and also the substitution of Co for Fe.

Determination of magnetic anisotropy in the LnTRENSAL complexes (Ln = Tb, Dy, Er) by torque magnetometry.

We report here a study about the magnetic anisotropy of the LnTRENSAL complexes (Ln = Tb, Dy, Er) performed by using cantilever torque magnetometry and electron paramagnetic resonance. For all of the compounds, we extracted a set of crystal-field parameters to obtain the energy-level splitting of the ground-state multiplet.

Crystal field simulation and NMR study of19F in a EuF3Van Vleck paramagnet

The temperature dependence of the nuclear spin-lattice relaxation rate of 19F nuclei is measured for a powder sample of a EuF3 Van Vleck paramagnet, in a broad temperature range (55–300 K). The increase in the nuclear relaxation rate observed at T > 100 K is caused by fluctuations in the magnetic fields, induced at the fluorine nuclei by the magnetic moments of the europium ions, the lifetime of which is determined by a two-phonon relaxation process with input from the first excited state of the electron shell of Eu3+ ions (Δ1 = 370 K). The set of crystal field parameters allowing for a satisfactory description of the electron energy spectrum of the Eu3+ ions in the EuF3 crystal, is calculated within the framework of the semi-phenomenological exchange charge model.

Comparative analysis of crystal-field parameters for rare-earth ions at monoclinic sites in AB(WO4)2 crystals: II. Pr3+ and Nd3+ ions in KRE(WO4)2 (RE = Y or Gd), Pr3+ ions in M+Bi(XO4)2 (M+ = Li or Na and X = W or Mo), and Nd3+ ions in NaBi(WO4)2 and AgNd(WO4)2

In part I, the crystal-field (CF) parameter (CFP) sets for important potential solid state laser systems Tm3+, Ho3+, and Er3+ ions in KGd(WO4)2 and Tm3+ ions in KLu(WO4)2 were thoroughly revisited using a general framework for the analysis of CF levels and CFP modeling. In this part the non-standard CFP sets for Pr3+ and Nd3+ ions in KR(WO4)2 (R = Y or Gd) and the standard CFP sets for Pr3+ ions in M+Bi(XO4)2 (M+ = Li or Na and X = W or Mo) and Nd3+ ions in the related systems NaBi(WO4)2 and AgNd(WO4)2 are analyzed. Due to structural similarity of the hosts, the CFP values for a given trivalent rare-earth (RE3+) ion should be quite close in these systems. However, the fitted (and model) CFP sets appear disparate for the systems in question. The standardization criteria are utilized to ensure direct comparability of the apparently disparate CFP sets reported in the literature. The CFP sets standardized by us are compared with the originally standard CFP sets for Pr3+ and Nd3+ ions in related AB(XO4)2 systems. Following part I, we argue that meaningful analysis of the mixed CFP sets, i.e. standard and non-standard ones, must take into account the intrinsic features of CF Hamiltonians for orthorhombic and lower symmetry cases, which have not been fully recognized in the literature as yet. The model or fitted CFP sets that belong to disparate regions in the CFP space are intrinsically incompatible, i.e. such sets should not be directly compared. The correlated alternative CFP sets are calculated using monoclinic standardization transformations. The closeness of the standardized CFP sets is assessed in a quantitative way using the closeness factors and the norms ratios. Comparative analysis of the monoclinic CFP sets reported for the titled ion–host systems is carried out and several inconsistencies in the previous studies are clarified. The CFP sets determined by standardization are utilized as starting sets for applications of the multiple correlated fitting technique to independently obtain and additionally verify the fitted CFPs based on published energy levels data. Multiple correlated fittings offer an advantage over the single-fitting tactics by enabling an improved fine-tuning of the final fitted CFPs as well as their interpretation and comparability with the sets obtained by others. The present consistent methodology may enable better understanding of the intricate aspects inherent in the spectroscopic studies for other ion–host systems exhibiting orthorhombic, monoclinic, and triclinic site symmetry.

SIMPRE: A software package to calculate crystal field parameters, energy levels, and magnetic properties on mononuclear lanthanoid complexes based on charge distributions

This work presents a fortran77 code based on an effective electrostatic model of point charges around a rare earth ion. The program calculates the full set of crystal field parameters, energy levels spectrum, and wave functions, as well as the magnetic properties such as the magnetization, the temperature dependence of the magnetic susceptibility, and the Schottky contribution to the specific heat. It is designed for real systems that need not bear ideal symmetry and it is able to determine the easy axis of magnetization. Its systematic application to different coordination environments allows magneto-structural studies. The package has already been successfully applied to several mononuclear systems with single-molecule magnetic behavior. The determination of effective point charge parameters in these studies facilitates its application to new systems. In this article, we illustrate its usage with two example studies: (a) an ideal cubic structure coordinating a lanthanoid ion and (b) a system with slow relaxation of the magnetization, LiHo(x)Y((1-x))F(4).

Systematization of crystal field parameters for trivalent rare-earth (RE3+) ions at orthorhombic sites in selected laser materials—standardization approach

The crucial intrinsic features of orthorhombic crystal field (CF) parameter (CFP) sets, i.e. existence of alternative disparate sets, which belong to different regions in the CFP space, and incorrectness of comparison of such CFP sets, are elucidated. Several cases of incorrect comparisons of fitted CFP sets obtained by various authors have been revealed by survey of spectroscopic studies of rare-earth ions at orthorhombic sites in technologically important crystals. This finding indicates that these features are not fully realized and calls for clarification of implications of these features for interpretation of spectroscopic data. For this purpose, we outline standardization approach for dealing with intrinsically incompatible CFP sets. It is shown that direct comparisons of disparate yet correlated CFP sets lead to incorrect conclusions concerning the relative magnitudes of CFPs and structural implications. The axis systems in which the theoretical CFPs are expressed or which are assigned to the fitted CFPs are also discussed. The standardization approach is employed for systematization and comparative analysis of the orthorhombic non-standard CFP sets for selected systems, i.e. Er3+:SrLaAlO4, Ce3+:Ce2Ge2In, Eu3+:BaFCl, Er3+:LiKGdF5, Eu3+:SBN, Pr3+:K2PrCl5 and Pr3+:K2YF5. The present results may facilitate future spectroscopic determination of CFPs and increase reliability of fitted and theoretical CFPs for fN ions at orthorhombic sites.

Investigation of the local structure and EPR spectra for Nd3+ in Bi4Ge3O12

On the basis of complete energy matrices for a 4f3 configuration ion in trigonal symmetry ligand-field, the optical and EPR spectra of Nd3+ center in Bi4Ge3O12 have been reasonably explained. The results indicate that the Nd3+ ion do not occupy the actual Bi3+ site, but departure from the ideal host position along the C3 axis by about 0.07Å. The new set of crystal-field parameters that can well account for the Stark levels and EPR parameters have been obtained from the superposition model. Moreover, the influence of orbital reduction factor k and local distortion parameter ΔZ on EPR parameters is analyzed.

Trends in orthorhombic crystal field parameters for trivalent rare-earth ions in high-Tc superconductors REBa2Cu3O7−δ – Correct interpretation based on standardization

Trends in orthorhombic crystal field parameters (CFPs) reported for RE3+ ions in high-Tc superconductors REBa2Cu3O7−δ are considered. The cases of trends based on the CFP sets belonging to different regions of CF parameter space are identified and clarified. The crucial feature of such correlated alternative CFP sets is their intrinsic incompatibility. This makes meaningless direct comparisons of such CFP sets and thus presentations of CFP trends involving a mixture of alternative CFP sets. The aim of this paper is to ascertain that correct interpretation of trends in orthorhombic CFPs must be based on standardization. Examples of graphs inappropriately representing trends in orthorhombic CFPs reported for REBa2Cu3O7−δ compounds are considered and the corrected graphs based on the standardized CFP sets are provided.