Explanation

This section provides background knowledge on the Adsorption Information Format (AIF) format and the NOMAD plugin that parses it.

What is the AIF Format?

The Adsorption Information Format (AIF) is a standardized archive format for adsorption data, developed to ensure consistent reporting of porous materials adsorption experiments. It provides a universal standard for archiving adsorption data as described in the referenced publications.

The AIF format addresses the challenges of inconsistent data representation in adsorption studies by providing a structured, machine-readable format that includes:

• Experimental metadata
• Sample information
• Adsorption/desorption data points
• Simulation data (when applicable)
• Citation and versioning information

AIF Structure

The AIF format is organized into several logical sections:

1. Experimental Metadata

Contains information about the experiment setup, including:

• Operator details
• Experiment date and instrument used
• Adsorptive substance information
• Experimental conditions (temperature, method, etc.)

2. Sample Information

Describes the sample characteristics:

• Sample mass and density
• Unique identifiers
• Degassing conditions and summary

3. Adsorption/Desorption Data

The core data points including:

• Equilibrium pressures
• Loadings (amount adsorbed)
• Thermodynamic properties (enthalpy)
• Saturation pressures

4. Simulation Data

Information about computational simulations when applicable:

• Simulation codes and dates
• Force field details
• Input files and sampling methods

5. Citation and Versioning

References and version control information:

• DOI references
• Version tracking of the AIF format

AIF Metadata Fields

Unit Fields

Field	NOMAD Equivalent	Description	Data Type
_units_pressure	aif_data_pressure_units	Units for pressure measurements	string
_units_temperature	aif_data_temperature_units	Units for temperature measurements	string
_units_mass	aif_data_mass_units	Units for mass measurements	string
_units_density	aif_data_density_units	Units for density measurements	string
_units_time	aif_data_time_units	Units for time measurements	string
_units_loading	aif_data_loading_units	Units for loading measurements	string
_units_energy	aif_data_energy_units	Units for energy measurements	string

Experimental Metadata Fields

Field	NOMAD Equivalent	Description	Data Type
_exptl_operator	aif_operator	Name of the person who ran the experiment	string
_exptl_date	aif_date	Date of the experiment (ISO 8601 format)	datetime
_exptl_instrument	aif_instrument	Instrument used for the experiment	string
_exptl_adsorptive	aif_adsorptive	Name of the adsorptive substance	string
_exptl_adsorptive_name	aif_adsorptive_name	Secondary identifier for adsorptive	string
_exptl_temperature	aif_temperature	Experiment temperature	float
_exptl_method	aif_method	Method used to determine amount adsorbed	string
_exptl_isotherm_type	aif_isotherm_type	Isotherm type (absolute, excess, net)	string
_exptl_p0	aif_saturation_pressure	Saturation pressure at experiment temperature	float
_exptl_digitizer	aif_digitizer	Person who digitized the experiment	string

Sample Information Fields

Field	NOMAD Equivalent	Description	Data Type
_adsnt_sample_mass	aif_sample_mass	Mass of the sample	float
_adsnt_sample_density	aif_sample_density	Density of the sample	float
_adsnt_sample_id	aif_sample_id	Unique identifying code for sample	string
_adsnt_material_id	aif_sample_material_id	Designated name for the material	string
_adsnt_info	aif_info	Secondary identifier	string
_adsnt_hashkey	aif_hashkey	Secondary identifier	string
_adsnt_degas_summary	aif_degas_summary	Summary of degas conditions	string
_adsnt_degas_temperature	aif_degas_temperature	Degas temperature	float
_adsnt_degas_time	aif_degas_time	Degas time	float with unit

Adsorption/Desorption Data Fields

Pressure and Saturation Data

Field	NOMAD Equivalent	Description	Data Type
_adsorp_pressure / _desorp_pressure	aif_data_pressure	Equilibrium pressure	array of floats
_adsorp_p0 / _desorp_p0	aif_data_saturation_pressure	Saturation pressure at experiment temperature	array of floats
_adsorp_fugacity / _desorp_fugacity	aif_data_fugacity	Fugacity values	array of floats

Loading Data

Field	NOMAD Equivalent	Description	Data Type
_adsorp_amount / _desorp_amount	aif_data_amount	Amount adsorbed (loading)	array of floats
_adsorp_loading / _desorp_loading	aif_data_amount	Deprecated field for loading	array of floats
_adsorp_amount_excess / _desorp_amount_excess	aif_data_amount_excess	Excess amount adsorbed	array of floats
_adsorp_amount_absolute / _desorp_amount_absolute	aif_data_amount_absolute	Absolute amount adsorbed	array of floats
_adsorp_amount_net / _desorp_amount_net	aif_data_amount_net	Net amount adsorbed	array of floats
_adsorp_enthalpy / _desorp_enthalpy	aif_data_enthalpy	Enthalpy of adsorption/desorption	array of floats

Simulation Data Fields

Field	NOMAD Equivalent	Description	Data Type
_simltn_code	aif_simltn_code	Simulation code identifier	string
_simltn_date	aif_simltn_date	Date of simulation	datetime
_simltn_size	aif_simltn_size	Simulation size parameters	string
_simltn_forcefield_adsorptive	aif_simltn_forcefield_adsorptive	Adsorptive force field details	string
_simltn_forcefield_adsorbent	aif_simltn_forcefield_adsorbent	Adsorbent force field details	string
_simltn_input_files	aif_simltn_input_files	Links to input files	string
_simltn_sampling	aif_simltn_sampling	Sampling algorithm used	string
_simltn_lot	aif_simltn_lot	Level of theory used	string

Citation and Versioning Fields

Field	NOMAD Equivalent	Description	Data Type
_audit_aif_version	aif_version	Version of AIF data names	string
_citation_doi	aif_citation_doi	DOI of cited work	string
_citation_source	aif_citation_source	Source of cited work	string

Unit Handling in AIF

The AIF format supports flexible unit specification through various _units_* fields. These fields are crucial for proper data interpretation and conversion:

• Pressure units: Commonly "kPa", "torr", "Pa", "Pascal"
• Temperature units: Typically "K", "k", "kelvin"
• Mass units: Usually "g", "kg", "gram", "kilogram"
• Density units: Often "g/cc", "kg/cc", "gram/centimeter**3"
• Time units: Standard "s", "min", "h", "second", "minute", "hour"
• Loading units: Frequently "MOL-PER-KiloGM", "mmolg-1", "mol/kg", "mmol/g"
• Energy units: Commonly "KiloJ-PER-MOL", "kJ/mole"

The parser includes robust unit conversion logic to standardize these variations into NOMAD's standard unit system, ensuring compatibility across different data sources.

NOMAD Integration

The AIF parser plugin integrates with NOMAD by:

1. Creating structured data in NOMAD's schema system
2. Supporting unit conversion for various physical quantities
3. Generating visualizations of adsorption data
4. Making data searchable through NOMAD's query system
5. Providing consistent metadata handling

Best Practices

When working with AIF files and the NOMAD plugin:

1. Ensure all required metadata fields are populated
2. Use consistent unit naming conventions
3. Validate data integrity before parsing
4. Leverage NOMAD's search capabilities for data discovery
5. Take advantage of the plugin's visualization features for data analysis

References

• AIF Official Dictionary
• AIF Development Team Repository
• AIF Official Website
• A Universal Standard Archive File for Adsorption Data
• Best-Practice Reporting for Porous Materials Adsorption Data