Citation: A RESTful API for exchanging materials data in the AFLOWLIB.org consortium. Computational Materials Science, Volume 93, October 2014, Pages 178-192. Richard H. Taylor, Frisco Rose, Cormac Toher, Ohad Levy, Kesong Yang, Marco Buongiorno Nardelli, Stefano Curtarolo.
URL: http://www.sciencedirect.com/science/article/pii/S0927025614003322
DOI: 10.1016/j.commatsci.2014.05.014
auid
Description: “AFLOWLIB Unique Identifier” for the entry, AUID, which can be used as a publishable object identifier1).
Type: string
Example: auid=aflow:e9c6d914c4b8d9ca
Request syntax: $aurl/?auid
aurl
Description: “AFLOWLIB Uniform Resource Locator” returns the AURL of the entry. The web server is separated from the web directory with “:”. This tautological keyword, aurl
returning itself, is useful for debugging and hyperlinking purposes.
Type: string
Example: aurl=aflowlib.duke.edu:AFLOWDATA/LIB3_RAW/Bi_dRh_pvTi_sv/T0003.ABC:LDAU2
Request syntax: $aurl/?aurl
data_api
Description: “AFLOWLIB” version of the entry, API. This article describes version 1.0 of the REST-API.
Type: string
Example: data_api=aapi1.0
Request syntax: $aurl/?data_api
keywords
Description: This includes the list of keywords available in the entry, separated by commas. All of the keywords can be requested to the database. The request keywords
should be the first one made, so that the reader is made aware of the available keywords.
Type: List of strings
separated by “,”
Example: keywords=aurl,auid,loop,code,compound,prototype…
Request syntax: $aurl/?keywords
aflowlib_entries
Description: For projects and set-layer entries (see Figure 1 of the REST API paper2)), aflowlib_entries
lists the available sub-entries which are associated with the $aurl
of the subdirectories.
Type: Set of strings
separated by “,”
Example: aflowlib_entries=AgAl,AgAs,AgAu,AgB_h,AgBa_sv,AgBe_sv,AgBi_d,AgBr,AgCa_sv,
Request syntax: $aurl/?aflowlib_entries
aflowlib_entries_number
Description: For projects and set-layer entries, aflowlib_entries
lists the available sub-entries which are associated with the $aurl
of the subdirectories. By parsing $aurl/?aflowlib_entries
(containing $aurl/aflowlib_entries_number
entries) the user finds the further locations to interrogate.
Type: number
Example: aflowlib_entries_number=1524
Request syntax: $aurl/aflowlib_entries_number
aflowlib_date
Description: Returns the date of the AFLOW post-processor which generated the entry for the library. This entry is useful for debugging and regression purposes.
Type: string
Example: aflowlib_date=20140204_13:10:39_GMT-5
Request syntax: $aurl/?aflowlib_date
aflow_version
Description: Returns the version number of AFLOW used to perform the calculation. This entry is useful for debugging and regression purposes.
Type: string
Example: aflow_version=aflow30641
Request syntax: $aurl/?aflow_version
author
Description: Returns the name (not necessarily an individual) and affiliation associated with authorship of the data. Multiple entries are separated by commas. Spaces are substituted with “_” to aid parsing.
Type: List of strings
separated by “,”
Example: author=Marco_Buongiorno_Nardelli,Ohad_Levy,Jesus_Carrete
Request syntax: $aurl/?author
calculation_cores
Description: Number of processors/cores, maximum memory, total time used for the calculation.
Type: number
Units: adimensional
Example: calculation_cores=32
Request syntax: $aurl/?calculation_cores
calculation_memory
Description: Maximum memory used for the calculation.
Type: number
Units: Megabytes
Example: calculation_memory=8376.13
Request syntax: $aurl/?calculation_memory
calculation_time
Description: Total time used for the calculation.
Type: number
Units: seconds
Example: calculation_time=140713
Request syntax: $aurl/?calculation_time
corresponding
Description: Returns the name (not necessarily an individual) and affiliation associated with the data origin concerning correspondence about data. Multiple entries are separated by commas. Spaces are substituted with “_” to aid parsing.
Type: List of strings
separated by “,”
Example: corresponding=M_Buongiorno_Nardelli_mbn@unt.edu
Request syntax: $aurl/?corresponding
data_source
Description: The layered structure of AFLOWLIB adapts to serve and translate data presented in other open databases. If this is the case, the source and language (API) of the data are given with these two keywords. When using non-AFLOWLIB data, due diligence is required to recognize the authorship of the original work, and not the serving database, merely.
Type: strings
Example: data_source=aflowlib
Request syntax: $aurl/?data_source
data_language
Description: The layered structure of AFLOWLIB adapts to serve and translate data presented in other open databases. If this is the case, the source and language (API) of the data are given with these two keywords. When using non-AFLOWLIB data, due diligence is required to recognize the authorship of the original work, and not the serving database, merely.
Type: strings
Example: data_language=translated
Request syntax: $aurl/?data_language
loop
Description: Informs the user of the type of post-processing that was performed.
Type: List of strings
separated by “,”
Example: loop=thermodynamics,bands,magnetic
Request syntax: $aurl/?loop
node_CPU_Cores
Description: Information about the node/cluster where the calculation was performed. Number of cores accessible to the calculation.
Type: number
Example: node_CPU_Cores=12
Request syntax: $aurl/?node_CPU_Cores
node_CPU_MHz
Description: Information about the speed of the node/cluster where the calculation was performed.
Type: number
Units: MHz
Example: node_CPU_MHz=2661
Request syntax: $aurl/?node_CPU_MHz
node_CPU_Model
Description: Information about the model of the node/cluster where the calculation was performed.
Type: string
Example: node_CPU_Model=Intel(R)_Xeon(R)_CPU_X5650_@_2.67GHz
Request syntax: $aurl/?node_CPU_Model
node_RAM_GB
Description: Information about the total memory accessible to the calculation in the node/cluster where the calculation was performed.
Type: number
Units: Gigabytes
Example: node_RAM_GB=48
Request syntax: $aurl/?node_RAM_GB
sponsor
Description: Returns information about funding agencies and other sponsors for the data. Multiple entries are separated by commas. Spaces are substituted with “_” to aid parsing.
Type: List of strings
separated by “,”
Example: sponsor=DOD_N000141310635,NIST_70NANB12H163
Request syntax: $aurl/?sponsor
agl_acoustic_debye
Description: Returns AGL acoustic Debye temperature. The acoustic Debye temperature is the Debye temperature
obtained by integrated only over the acoustic phonon modes. It can be obtained from the traditional
Debye temperature using the expression .
Type: number
Units: Kelvin
Example: agl_acoustic_debye=492
Request syntax: $aurl/?agl_acoustic_debye
agl_bulk_modulus_isothermal_300K
Description: Returns AGL isothermal bulk modulus at 300K and zero pressure.
Type: number
Units: GPa
Example: agl_bulk_modulus_isothermal_300K=96.6
Request syntax: $aurl/?agl_bulk_modulus_isothermal_300K
agl_bulk_modulus_static_300K
Description: Returns AGL static bulk modulus at 300K and zero pressure.
Type: number
Units: GPa
Example: agl_bulk_modulus_static_300K=99.59
Request syntax: $aurl/?agl_bulk_modulus_static_300K
agl_debye
Description: Returns AGL Debye temperature.
Type: number
Units: Kelvin
Example: agl_debye=620
Request syntax: $aurl/?agl_debye
agl_gruneisen
Description: Returns AGL Gruneisen parameter.
Type: number
Units: dimensionless
Example: agl_gruneisen=2.06
Request syntax: $aurl/?agl_gruneise
agl_heat_capacity_Cv_300K
Description: Returns AGL heat capacity at constant volume (CV) at 300K and zero pressure.
Type: number
Units: kB/cell
Example: agl_heat_capacity_Cv_300K=4.901
Request syntax: $aurl/?agl_heat_capacity_Cv_300K
agl_heat_capacity_Cp_300K
Description: Returns AGL heat capacity at constant pressure (Cp) at 300K and zero pressure.
Type: number
Units: kB/cell
Example: agl_heat_capacity_Cp_300K=5.502
Request syntax: $aurl/?agl_heat_capacity_Cp_300K
agl_thermal_conductivity_300K
Description: Returns AGL thermal conductivity at 300K.
Type: number
Units: W/m*K
Example: agl_thermal_conductivity_300K=24.41
Request syntax: $aurl/?agl_thermal_conductivity_300K
agl_thermal_expansion_300K
Description: Returns AGL thermal expansion at 300K and zero pressure.
Type: number
Units: 1/K
Example: agl_thermal_expansion_300K=4.997e-05
Request syntax: $aurl/?agl_thermal_expansion_300K
ael_bulk_modulus_reuss
Description: Returns AEL bulk modulus as calculated using the Reuss average.
Type: number
Units: GPa
Example: ael_bulk_modulus_reuss=105.315
Request syntax: $aurl/?ael_bulk_modulus_reuss
ael_bulk_modulus_voigt
Description: Returns AEL bulk modulus as calculated using the Voigt average.
Type: number
Units: GPa
Example: ael_bulk_modulus_voigt=105.315
Request syntax: $aurl/?ael_bulk_modulus_voigt
ael_bulk_modulus_vrh
Description: Returns AEL bulk modulus as calculated using the Voigt-Reuss-Hill (VRH) average.
Type: number
Units: GPa
Example: el_bulk_modulus_vrh=105.315
Request syntax: $aurl/?ael_bulk_modulus_vrh
ael_elastic_anistropy
Description: Returns AEL elastic anisotropy.
Type: number
Units: dimensionless
Example: ael_elastic_anistropy=0.000816153
Request syntax: $aurl/?ael_elastic_anisotropy
ael_poisson_ratio
Description: Returns AEL Poisson ratio.
Type: number
Units: dimensionless
Example: ael_poisson_ratio=0.21599
Request syntax: $aurl/?ael_poisson_ratio
ael_shear_modulus_reuss
Description: Returns AEL shear modulus as calculated using the Reuss average.
Type: number
Units: GPa
Example: ael_shear_modulus_reuss=73.7868
Request syntax: $aurl/?ael_shear_modulus_reuss
ael_shear_modulus_voigt
Description: Returns AEL shear modulus as calculated using the Voigt average.
Type: number
Units: GPa
Example: ael_shear_modulus_voigt=73.7989
Request syntax: $aurl/?ael_shear_modulus_voigt
bader_atomic_volumes
Description: Returns the volume of each atom of the primitive cell as calculated by the Bader Atoms in Molecules Analysis. This volume encapsulates the electron density associated with each atom above a threshold of 0.0001 electrons.
Type: String of numbers separated by ','
Units: Angstroms3
Example: bader_atomic_volumes=28.1396,25.6828,25.6828,77.1826
Request syntax: $aurl/?bader_atomic_volumes
bader_net_charges
Description: Returns the partial charge per atom of the primitive cell as calculated by the Bader Atoms in Molecules Analysis.
Type: String of numbers separated by ','
Units: electrons
Example: bader_net_charges=0.6828,0.6577,0.6577,-1.9982
Request syntax: $aurl/?bader_net_charges
ael_shear_modulus_vrh
Description: Returns AEL shear modulus as calculated using the Voigt-Reuss-Hill (VRH) average.
Type: number
Units: GPa
Example: ael_shear_modulus_vrh=73.7929
Request syntax: $aurl/?ael_shear_modulus_vrh
Bravais_lattice_orig
Description: Returns the Bravais lattice of the original unrelaxed3) structure before the calculation.
Type: string
Example: Bravais_lattice_orig=MCLC
Request syntax: $aurl/?Bravais_lattice_orig
Tolerance: Calculations of lattices (Brillouin zones), prototypes, and symmetries (point/factor/space groups) are based on different algorithms and require different sets of tolerances. To guarantee self-consistency of the results, initial tolerances are set to very stringent values (e.g., 10-4% for distances, 102% for angles, 10-4% for spectral radii of mapping matrices, etc.) and slowly increased alternatingly (by a factor of 2) until self- consistency is found amongst geometrical descriptors. The final tolerances are usually of the order of ~0.5% for distances and ~1% for angles.
Bravais_lattice_relax
Description: Returns the Bravais lattice4) of the relaxed structure after the calculation.
Type: string
Example: Bravais_lattice_relax=MCLC
Request syntax: $aurl/?Bravais_lattice_relax
Tolerance: Calculations of lattices (Brillouin zones), prototypes, and symmetries (point/factor/space groups) are based on different algorithms and require different sets of tolerances. To guarantee self-consistency of the results, initial tolerances are set to very stringent values (e.g., 10-4% for distances, 102% for angles, 10-4% for spectral radii of mapping matrices, etc.) and slowly increased alternatingly (by a factor of 2) until self- consistency is found amongst geometrical descriptors. The final tolerances are usually of the order of ~0:5% for distances and ~1% for angles.
code
Description: Returns the software name and version used to perform the simulation.
Type: string
Example: code=vasp.4.6.35
Request syntax: $aurl/?code
composition
Description: Returns a comma delimited composition description of the structure entry in the calculated cell.
Type: List of number
separated by “,”
Example: composition=2,6,6
(For a A2B6C6 compound.)
Request syntax: $aurl/?composition
compound
Description: Similar to composition
. Returns the composition description of the compound in the calculated cell.
Type: Set of {string number}
Example: compound=Co2Er6Si6
Request syntax: $aurl/?compound
density
Description: Returns the mass density.
Type: number
Units: grams/cm3
Example: density=7.76665
Request syntax: $aurl/?density
dft_type
Description: Returns information about the pseudopotential type, the exchange correlation functional used (normal or hybrid) and use of GW.
Type: Set of strings
separated by “,”
Example: If the calculations were performed with VASP5), the entry could include “US”, “GGA”, “PAW LDA”, “PAW GGA”, “PAW PBE” , “GW”, “HSE06” (February 2014).
Example: dft_type=PAW_PBE,HSE06
Request syntax: $aurl/?dft_type
eentropy_cell
Description: Returns the electronic entropy of the unit cell used to converge the ab initio calculation (smearing).
Type: number
Units: Natural units of the $code
, e.g., eV or Ry (eV/atom or Ry/atom) if the calculations were performed
with VASP or QE, respectively.
Example: eentropy_cell=0.0011
Request syntax: $aurl/?eentropy_cell
eentropy_atom
Description: Returns the electronic entropy per atom of the unit cell used to converge the ab initio calculation (smearing).
Type: number
Units: Natural units of the $code
, e.g., eV or Ry (eV/atom or Ry/atom) if the calculations were performed
with VASP or QE, respectively.
Example: eentropy_atom=0.0003
Request syntax: $aurl/?eentropy_atom
Egap
Description: Band gap calculated with the approximations and pseudopotentials described by other keywords. This quantity is determined by tracking the valence band eigenvalue occupancies. For spin-polarized systems, this is the net gap (the gap between the highest occupied state for either spin and the lowest unoccupied state for either spin).
Type: number
Units: eV
Example: Egap=2.5
Request syntax: $aurl/?Egap
Egap_type
Description: Given a band gap, this keyword describes if the system is a metal, a semi-metal, an insulator with direct or indirect band gap.
Type: string
Example: Egap_type=insulator_direct
Request syntax: $aurl/?Egap_type
energy_cell
Description: Returns the total ab initio energy of the unit cell E.
Type: number
Units: Natural units of the $code
, e.g., eV or Ry (eV/atom or Ry/atom) if the calculations were performed
with VASP or QE, respectively.
Example: energy_cell=-82.1656
Request syntax: $aurl/?energy_cell
energy_atom
Description: Returns the energy per atom- the value of energy_cell
/N.
Type: number
Units: Natural units of the $code
, e.g., eV or Ry (eV/atom or Ry/atom) if the calculations were performed
with VASP or QE, respectively.
Example: energy_atom=-5.13535
Request syntax: $aurl/?energy_atom
energy_cutoff
Description: Set of energy cut-os used during the various steps of the calculations.
Type: Set of strings
separated by “,”
Units: Natural units of the $code
, e.g., eV or Ry (eV/atom or Ry/atom) if the calculations were performed
with VASP or QE, respectively.
Example: energy_cutoff=384.1,384.1,384.1
Request syntax: $aurl/?energy_cutoff
enthalpy_cell
Description: Returns the enthalpy of the system of the unit cell H = E + PV.
Type: number
Units: Natural units of the $code
, e.g., eV or Ry (eV/atom or Ry/atom) if the calculations were performed
with VASP or QE, respectively.
Example: enthalpy_cell=-82.1656
Request syntax: $aurl/?enthalpy_cell
enthalpy_atom
Description: Returns the enthalpy per atom- the value of enthalpy_cell
/N.
Type: number
Units: Natural units of the $code
, e.g., eV or Ry (eV/atom or Ry/atom) if the calculations were performed
with VASP or QE, respectively.
Example: enthalpy_atom=-5.13535
Request syntax: $aurl/?enthalphy_atom
enthalpy_formation_cell
Description: Returns the formation enthalpy per unit cell (
per atom). For compounds
with
atoms per cell,
this is defined as:
(in the
case with
and
we have
).
Type: number
Units: Natural units of the $code
, e.g., eV or Ry (eV/atom or Ry/atom) if the calculations were performed
with VASP or QE, respectively.
Example: enthalpy_formation_cell=-33.1587
Request syntax: $aurl/?enthalpy_formation_cell
enthalpy_formation_atom
Description: Returns the formation enthalpy per unit cell (
per atom). For compounds
with
atoms per cell,
this is defined as:
(in the
case with
and
we have
).
Type: number
Units: Natural units of the $code
, e.g., eV or Ry (eV/atom or Ry/atom) if the calculations were performed
with VASP or QE, respectively.
Example: enthalpy_formation_atom=-0.720841
Request syntax: $aurl/?enthalpy_formation_atom
entropic_temperature
Description: Returns the entropic temperature as defined in Curtarolo et al.6) and Hart et al.7) for the structure. The analysis of
formation enthalpy is, by itself, insufficient to compare alloy stability at different concentrations and their
resilience toward high-temperature disorder. The formation enthalpy represents the ordering-strength of a
mixture against decomposition into its pure constituents at the appropriate concentrations
. (
is negative for compound forming systems). However, it does not contain information about its resilience against disorder, which is captured by the entropy of the system. To quantify this resilience we define the entropic temperature for each compound as:
where the sign is chosen so that a positive temperature is needed for competing against compound stability.
This definition assumes an ideal scenario8) where the entropy is
.
is a concentration-maximized formation enthalpy weighted by the inverse of its entropic contribution.
Its maximum
represents the deviation of a system convex-hull from
the purely entropic free-energy hull,
, and hence
the ability of its ordered phases to resist the temperature-driven deterioration into a disordered mixture
exclusively promoted by configurational-entropy.
Type: number
Units: Kelvin
Example: entropic_temperature=1072.1
Request syntax: $aurl/?entropic_temperature
files
Description: Provides access to the input and output les used in the simulation (provenance data).
Type: List of strings
separated by “,”
Example: files=Bi_dRh_pv.33.cif,Bi_dRh_pv.33.png,CONTCAR.relax,CONTCAR.relax1…,
DOSCAR.static.bz2,EIGENVAL.bands.bz2,KPOINTS.bands.bz2,aflow.in,edata.bands.out,…
edata.orig.out,edata.relax.out,…
Request syntax: $aurl/?files
Description: Once the “files
” list has been parsed, each file can be accessed with $aurl/file
(note no “?”
for accessing individual files).
forces
Description: Final quantum mechanical forces (Fi; Fj; Fk) in the notation of the code.
Type: Triplets (number,number,number
) separated by “;” for each atom in the unit cell
Units: Natural units of the $code
, e.g., eV/Å or a.u. if the calculations were performed
with VASP or QE, respectively.
Example: forces=0,-0.023928,0.000197;0,0.023928,-0.000197;…
Request syntax: $aurl/?forces
geometry
Description: Returns geometrical data describing the unit cell in the usual notation, where
.
Type: Sixtuplet (number,number,number,number,number,number
)
Units: a, b, c are the natural units of the $code
, e.g., Å or a.u. (Bohr) if the calculations were performed
with VASP or QE, respectively. α, β, γ are in degrees.
Example: geometry=18.82,18.82,18.82,32.41,32.41,32.41
Request syntax: $aurl/?geometry
lattice_system_orig
Description: Return the lattice system9)10) and lattice variation (Brillouin zone) of the original-unrelaxed structure before the calculation. See references11)12) for the lattice variation and Brillouin zones notations.
Type: string
Example: lattice_system_orig=rhombohedral
Request syntax: $aurl/?lattice_system_orig
lattice_variation_orig
Description: Return the lattice system13)14) and lattice variation (Brillouin zone) of the original-unrelaxed structure before the calculation. See references15)16) for the lattice variation and Brillouin zones notations.
Type: string
Example: lattice_variation_orig=RHL1
Request syntax: $aurl/?lattice_variation_orig
lattice_system_relax
Description: Return the lattice system17)18) and lattice variation (Brillouin zone) of the relaxed structure after the calculation. See references19)20) for the lattice variation and Brillouin zones notations.
Type: string
Example: lattice_system_relax=monoclinic
Request syntax: $aurl/?lattice_system_relax
lattice_variation_relax
Description: Return the lattice system21)22) and lattice variation (Brillouin zone) of the relaxed structure after the calculation. See references23)24) for the lattice variation and Brillouin zones notations.
Type: string
Example: lattice_variation_relax=MCLC1
Request syntax: $aurl/?lattice_variation_relax
kpoints
Description: Set of k-point meshes uniquely identifying the various steps of the calculations, e.g. relaxation, static and electronic band structure (specifying the k-space symmetry points of the structure).
Type: Set of numbers
and strings
separated by “,” and “;”
Example: kpoints=10,10,10;16,16,16;G-X-W-K-G-L-U-W-L-K+U-X
Request syntax: $aurl/?kpoints
ldau_TLUJ
Description: This vector of numbers contains the parameters of the “DFT+U” calculations, based on a corrective functional inspired by the Hubbard model25)26). See references for the standard values in the AFLOWLIB.org library27)28). There are four fields (T
;{L
};{U
};{J
}), separated by “;”. The first field indicates the type (T
) of the DFT+U corrections: type=1, the rotationally invariant version introduced by Liechtenstein et al.29); type=2, the simplified rotationally invariant version introduced by Dudarev et al.30). The second field indicates the l-quantum number ({L}, one number for each species separated by “,”) for which the on-site interaction is added (-1=neglected, 0=, 1=
, 2=
, 3=
). The third field lists the effective on-site Coulomb interaction parameters ({U}, one number for each species separated by “,”). The fourth field species the effective on-site exchange interaction parameters ({J}, one number for each species separated by “,”). Although more compact, the convention is similar to the VASP notation31).
Units: a-dimensional; {adimensional}; {eV}; {eV}
Type: number
;{number
};{
number
}{
number
}
Example: ldau_TLUJ=2;2,0,0;5,0,0;0,0,0
Request syntax: $aurl/?ldau_TLUJ
natoms
Description: Returns the number of atoms in the unit cell of the structure entry. The number can be non integer if partial occupation is considered within appropriate approximations.
Type: number
Example: natoms=12
Request syntax: $aurl/?natoms
nbondxx
Description: Nearest neighbors bond lengths of the relaxed structure per ordered set of species .
For pure systems:
;
for binaries:
;
for ternaries:
and so on.
Type: Set of
numbers
Units: Natural units of the $code
, e.g., Å or a.u. (Bohr) if the calculations were performed with VASP or QE, respectively.
Example: nbondxx=1.2599,1.0911,1.0911,1.7818,1.2599,1.7818
(for a three species entry)
Request syntax: $aurl/?nbondxx
nspecies
Description: Returns the number of species in the system (e.g., binary = 2, ternary = 3, etc.).
Type: number
Example: nspecies=3
Request syntax: $aurl/?nspecies
Pearson_symbol_orig
Description: Returns the Pearson symbol32)33) of the original-unrelaxed structure before the calculation.
Type: string
Example: Pearson_symbol_orig=mS32
Request syntax: $aurl/?Pearson_symbol_orig
Tolerance: See discussion about tolerances in entry Bravais_lattice_orig
.
Pearson_symbol_relax
Description: Returns the Pearson symbol34)35) of the relaxed structure after the calculation.
Type: string
Example: Pearson_symbol_relax=mS32
Request syntax: $aurl/?Pearson_symbol_relax
Tolerance: See discussion about tolerances in entry Bravais_lattice_orig
.
positions_cartesian
Description: Final Cartesian positions in the notation of the code.
Type: Triplets (number,number,number
) separated by “;” for each atom in the unit cell
Units: Natural units of the code
, e.g., in Cartesian coordinates (Ä) if the calculations were performed with {\small VASP}36).
Example: positions_cartesian=0,0,0;18.18438,0,2.85027;…
Request syntax: $aurl/?positions_cartesian
positions_fractional
Description: Final fractional positions with respect to the unit cell as specified in
$geometry
.
Type: Triplets (number,number,number
) separated by “;” for each atom in the unit cell
Example: positions_fractional=0,0,0;0.25,0.25,0.25;…
Request syntax: $aurl/?positions_fractional
pressure
Description: Returns the external pressure selected for the simulation.
Type: number
Units: Natural units of the $code
, e.g., kbar or a.u. (Ry/Bohr) if the calculations were performed with VASP or QE, respectively.
Example: pressure=10.0
Request syntax: $aurl/?pressure
prototype
Description: Returns the AFLOW unrelaxed prototype which was used for the calculation. The list can be
accessed with the command \aflow --protos
or by consulting the online links. The options are illustrated in
the AFLOW manual37). Note that during the calculation, unstable structures can deform and lead to different
relaxed configurations. It is thus imperative for the user to make an elaborate analysis of the final structure
to pinpoint the right prototype to report. Differences in Bravais lattices, Pearson symbol, space groups, for
the _orig
and _relax
versions are extremely useful for this task.
Type: string
Example: prototype=T0001.A2BC
Request syntax: $aurl/?prototype
Tolerance: See discussion about tolerances in entry Bravais_lattice_orig
.
PV_cell
Description: Pressure multiplied by volume of the unit cell.
Type: number
Units: Natural units of the $code
, e.g., eV or Ry (eV/atom or Ry/atom) if the calculations were performed
with VASP or QE, respectively.
Example: PV_cell=12.13
Request syntax: $aurl/?PV_cell
PV_atom
Description: Pressure multiplied by volume of the atom.
Type: number
Units: Natural units of the $code
, e.g., eV or Ry (eV/atom or Ry/atom) if the calculations were performed
with VASP or QE, respectively.
Example: PV_atom=3.03
Request syntax: $aurl/?PV_atom
scintillation_attenuation_length
Description: Returns the scintillation attenuation length of the compound in cm38)39).
Type: real number
Example: scintillation_attenuation_length=2.21895
Request syntax: $aurl/?scintillation_attenuation_length
sg (sg2)
Description: Evolution of the space group of the compound40)41). The first, second and third string represent space group name/number before the first, after the first, and after the last relaxation of the calculation.
Tolerance: sg
values are calculated with 3.0% and 0.5 deg tolerances for lengths and angles, respectively. (sg2
is with 1.5% and 0.25 deg). Symmetry is cross validated through the internal engines of AFLOW, PLATON, and FINDSYM.
Type: Triplet string,string,string
Example: sg=Fm-3m#225,Fm-3m#225,Fm-3m#225 (sg2=R-3c #167,R-3c #167,R-3c #167)
Request syntax: $aurl/?sg ($aurl/?sg2)
spacegroup_orig
Description: Returns the spacegroup number42) of the original-unrelaxed structure before the calculation.
Tolerance: Same as sg
.
Type: number
Example: spacegroup_orig=225
Request syntax: $aurl/?spacegroup_orig
spacegroup_relax
Description: Returns the spacegroup number43) of the relaxed structure after the calculation.
Tolerance: Same as sg
.
Type: number
Example: spacegroup_relax=225
Request syntax: $aurl/?spacegroup_relax
species
Description: Species of the atoms.
Type: List of strings
separated by “,”
Example: species=Y,Zn,Zr,
Request syntax: $aurl/?species
species_pp
Description: Pseudopotentials species.
Type: List of strings
separated by “,”
Example: species_pp=Y_sv,Zn,Zr_sv,
Request syntax: $aurl/?species_pp
species_pp_version
Description: Pseudopotential versions.
Type: List of strings
separated by “,”
Example: species_pp_version=Y_sv:PAW_PBE:06Sep2000,Zn:PAW_PBE:06Sep2000,Zr_sv:PAW_PBE:07Sep2000
Request syntax: $aurl/?species_pp_version
spin_cell
Description: For spin polarized calculations, the total magnetization of the cell.
Type: number
Units: Natural units of the $code
, e.g., (Bohr magneton).
Example: spin_cell=2.16419
Request syntax: $aurl/?spin_cell
spin_atom
Description: For spin polarized calculations, the total magnetization per atom.
Type: number
Units: Natural units of the $code
, e.g., (Bohr magneton).
Example: spin_atom=0.541046
Request syntax: $aurl/?spin_atom
spinD
Description: For spin polarized calculations, the spin decomposition over the atoms of the cell.
Type: List of numbers
separated by “,”
Units: Natural units of the $code
, e.g., (Bohr magneton).
Example: spinD=0.236,0.236,-0.023,1.005
Request syntax: $aurl/?spinD
spinD_magmom_orig
Description: For spin polarized calculations, string containing the values used to initialize the magnetic state for the ab initio calculation.
Type: String containing the instruction passed to the ab initio code with spaces substituted by “_”
Units: Natural units of the $code
.
Example: spinD_magmom_orig=+5_-5_+5_-5
Request syntax: $aurl/?spinD_magmom_orig
spinF
Description: For spin polarized calculations, the magnetization of the cell at the Fermi level.
Type: number
Units: Natural units of the $code
, e.g., (Bohr magneton).
Example: spinF=0.410879
Request syntax: $aurl/?spinF
stoichiometry
Description: Similar to composition, returns a comma delimited stoichiometry description of the structure entry in the calculated cell.
Type: List of number
separated by “,”
Example: stoichiometry=0.5,0.25,0.25
Request syntax: $aurl/?stoichiometry
valence_cell_std
Description: Returns standard valence44).
Type: number
Example: valence_cell_std=22
Request syntax: $aurl/?valence_cell_std
valence_cell_iupac
Description: Returns IUPAC valence, the maximum number of univalent atoms that may combine with the atoms45).
Type: number
Example: valence_cell_iupac=12
Request syntax: $aurl/?valence_cell_iupac
volume_cell
Description: Returns the volume of the unit cell (per atom in the unit cell).
Type: number
Units: Natural units of the $code
, e.g., Å3 or Bohr3 (Å3/atom or Bohr3/atom) if the calculations were performed with VASP or QE, respectively.
Example: volume_cell=100.984
Request syntax: $aurl/?volume_cell
volume_atom
Description: Returns the volume of the unit cell (per atom in the unit cell).
Type: number
Units: Natural units of the $code
, e.g., Å3
or Bohr3 (Å3/atom or Bohr3/atom) if the calculations were performed with VASP or QE, respectively.
Example: volume_atom=25.2461
Request syntax: $aurl/?volume_atom