The JuHemd (Jülich-Heusler-magnetic-database) is a collection of the magnetic phase transition types and transition temperatures (Tc) for experimentally documented Heusler and Heusler-like materials, as found by density functional calculations augmented by the Monte Carlo method, and as reported by experiment in the literature.
The database contains results on 400 compounds, many of them with different setups of the chemical order/disorder, totaling 776 systems. The ground state electronic structure was obtained by density functional theory calculations with the JuKKR code [1]. Two exchange-correlation functionals were employed: the local density approximation (LDA) [2] and the generalized gradient approximation (GGA) [3]. The chemical disorder was treated within the coherent-potential approximation [4,5]. For 306 materials (627 systems) with sizable magnetization, the Heisenberg exchange parameters were evaluated using the method of infinitesimal rotations [6] and the Tc was determined by our in-house Monte Carlo program (see e.g. [7]). The simulated data for all the compounds in the database are accompanied by experimental data published in the literature: the crystal structure, the lattice constant, the Tc and the character of the magnetic phase transition. The correlation between the experimental reports and the results for LDA and GGA functionals and the statistical analysis of these results will be published elsewhere.
[1] https://jukkr.fz-juelich.de and www.judft.de
[2] S. H. Vosko, L. Wilk, and M. Nusair, Canadian Journal of Physics 58, 1200 (1980).
[3] J. P. Perdew and Y. Wang, Phys. Rev. B 45, 13244 (1992).
[4] B. L. Gyorffy, Phys. Rev. B5, 2382 (1972)
[5] H. Ebert, D. Ködderitzsch and J. Minár, Reports on Progress in Physics 74, 096501 (2011).
[6] A. I. Liechtenstein, M. I. Katsnelson, V. P. Antropov, and V. A. Gubanov, Journal of Magnetism and Magnetic Materials 67, 65 (1987).
[7] R. Kováčik, P. Mavropoulos, and S. Blügel, Phys. Rev. B 91,014421 (2015).
The JuHemd.json database file contains a dictionary of the compounds with keys consisting of 4 chemical element symbols corresponding to the 4 sites at (0,0,0), (1/4,1/4,1/4), (1/2,1/2,1/2) and (3/4,3/4,3/4) in the Heusler face-centered cubic primitive unit cell. Single letter chemical symbols are augmented by '_' and voids are marked by 'Xx'.
The value for each compound is a dictionary containing the following keys:
- "DSIML-TcMCb": collects data of the LDA calculations for all structural setups of the particular compound;
- "DSIMG-TcMCb": collects data of the GGA calculations for all structural setups of the particular compound;
- "DEXP-Tc": contains the experimental reference data collected by Roman Kováčik from the scientific publications;
- "info": contains LaTeX formatted chemical formula and an integer encoded stoichiometric information;
- "struct_count": counts the occurrence of the individual structures.
The simulated "DSIM[L,G]-TcMCb" values are lists of different structural setups and the experimental "DEXP-Tc" values are lists of different experimental works. Each list entry is a nested dictionary with the following keys:
"cite": reference citation
- "doi": DOI if available;
- "yma": in YYYY-MM//author1/author2//authorN format.
"str": crystal structure information
- "label": label using Strukturbericht notation (if possible) and auxiliary sequence which encodes the chemical order/disorder;
- "lattice_constant": the lattice constant in Angstrom units;
- "cho": chemical order ("o") or disorder ("d");
- "mq": DEXP only; assessed quality of order/disorder determination: 0 (dubious), 1 (claimed / assumed / no evidence), 2 (qualitative), 3 (quantitative);
- "oq": DEXP only; order/disorder degree: P(erfect), G(ood), I(mperfect), U(ncertain), X (unknown / not reported);
the concentrations do not differ from the ideal values by more than 1.5% and 10% in case of P and G, respectively.
"db": raw database entries as lists
- "value": magnetic phase transition values (as entered into the database);
- "error": magnetic phase transition errors (as entered into the database);
- "method": method used to obtain the values;
- "condition": condition at which the values were obtained.
"data": post-processed database entries as lists
- "resval": list of critical temperature values (integer for "DSIM[L,G]-TcMCb", string for "DEXP-Tc");
- "mto": list of the corresponding magnetic phase transitions;
abbreviations:
? - uncertain / unknown
N - nonmagnetic
P - paramagnetic
SP - super paramagnetic
F - ferromagnetic, ferrimagnetic
CF - compensated ferrimagnetic
nCF - near-compensated ferrimagnetic
A[1-9,G]* - antiferromagnetic
S - spiral
s* - short-ranged
i* - imperfect
SG - spin glass (DEXP only)
SW - spin wave (DEXP only)
HSW - helical spin wave (DEXP only)
CG - cluster glass (DEXP only)
c* - canted (DEXP only)
- "mtf": DSIM only; magnetic phase transition obtained from the given feature;
abbreviations:
Md - magnetization derivative
Bx - Binder cumulant
Sp - magnetic susceptibility peak
Cp - heat capacity peak
sf - spin structure factor analysis
- the number that follows is the respective Monte Carlo supercell size
- l after the number refers to low resolution temperature scan
- n after the number refers to increased uncertainty due to unusually noisy data
- numbers after ':' refer to the sublattices used to extract the feature from
- "resmod": DEXP only; critical temperature value modifier;
- "errval": DEXP only; critical temperature error;
- "errmod": DEXP only; critical temperature error modifier.
From here on, DSIM only:
"str_expconf": structure was experimentally confirmed/suggested (1) or is hypothetical (0).
"system_dft": basic information about the ab-initio calculation
abbreviations:
KKR-GF - Korringa–Kohn–Rostoker Green-function
FP - full potential
SRA - scalar-relativistic approximation
LDA-VWN - local density approximation, Vosko-Wilk-Nusair
GGA-PW91 - generalized gradient approximation, Perdew-Wang
- "kpt": k-point mesh;
- "tau (K)": Fermi-Dirac smearing temperature in Kelvin;
- "rms_c": charge convergence condition;
- "rms_m": magnetization convergence condition.
"system_lattice":
- "a": Bravais lattice vectors;
- "b": reciprocal lattice vectors used to determine the magnetic structure.
"system_magnetic-structure":
- "gs": magnetic ground state determined from Monte Carlo simulations;
- "gs-list": list of unique states for different sublattices;
- "gs-verb": verbose description of the ground state including the q-vector;
- "mcss": Monte Carlo supercell size;
- "mtot_ai-mc": total magnetization in [ab-initio, Monte-Carlo];
- "mult-blattice": multiplier of "b" lattice to find the magnetic structure.
"system_rbasis": list of the site coordinates
"system_sites": list of the sites [site index (starting from 1), concentration, magnetic moment, element symbol]
"system_sites-eqgr": list of groups of symmetry equivalent sites