Molecular Descriptors Reference

Surfacia generates descriptors across molecular, atom-level, element-specific, and fragment-specific levels so that the final model can stay both compact and chemically interpretable.

• Size and Shape Descriptors
  • Overview
  • Descriptor Families
  • How to Interpret Them Quickly
  • Why They Matter
• Electronic Properties Descriptors
  • Overview
  • Available Descriptors
  • Calculation Methods
  • Applications
  • Validation and Quality Control
  • Integration with Experimental Data
  • Advanced Applications
  • References and Further Reading
• Surface Analysis Descriptors
  • Overview
  • Core Surface Properties
  • Common Statistics
  • Three MQSA Modes
  • How to Read the Names
  • What the Modes Are Good For
  • Why These Descriptors Matter

Overview

The descriptor system is designed to stay:

• physically grounded through wavefunction-derived surface properties

• hierarchical across global and local levels

• task-adaptive through three analysis modes

• interpretable after selection rather than only before modeling

Descriptor Categories

1. Size and Shape

Descriptors for physical extent, anisotropy, compactness, and planarity.

• molecular weight

• isosurface area

• molecular dimensions

• sphericity and asphericity

• radius of gyration related descriptors

2. Electronic Properties

Descriptors for frontier orbitals, orbital delocalization, and whole-molecule electronic structure.

• HOMO / LUMO

• HOMO-LUMO gap

• orbital delocalization indices

• global electronic indicators

3. Multi-Scale Surface Analysis

Descriptors for local surface electronics and task-specific interpretation.

• element-specific descriptors

• fragment-specific descriptors

• automated LOFFI atom-level and functional-group-level descriptors

How to Choose a Mode

Use the analysis mode that matches the amount of prior chemical knowledge you already have.

1. Mode 1: Element-Specific Best when one element is already suspected to be mechanistically important.

2. Mode 2: Fragment-Specific Best when a shared fragment, catalytic core, or pharmacophore is already known.

3. Mode 3: LOFFI Automated Best when you want broad exploratory analysis without hard-coding a mechanism first.

Naming Conventions

The feature names are intentionally systematic.

Prefix or Suffix	Meaning
Atom_	Atom-level global statistics over the molecular surface
Fun_	Functional-group-level statistics from automated LOFFI grouping
Fragment_	Descriptors calculated for a user-defined fragment
element-prefixed names	Descriptors aggregated around a selected element in Mode 1
*_min / *_max	Most chemically extreme sites or groups
*_mean / *_average	Overall average behavior
*_delta	Heterogeneity or spread across sites, groups, or atoms

Examples of Direct Chemical Meaning

Descriptor	Meaning	How to Read It
ALIE_min	Most nucleophilic region	Lower values often mean easier electron donation
ESP_max	Most electron-deficient region	Higher values often indicate stronger electrophilic character
Fun_ESP_delta	Electrostatic contrast between functional groups	Larger values suggest stronger intramolecular push-pull separation
Shape_Geometric_Asphericity	Pure geometric anisotropy	Higher values mean less sphere-like shape

Why This Matters for Modeling

Surfacia descriptors are meant to support more than predictive accuracy.

• they keep the model tied to recognizable chemistry

• they make SHAP plots easier to interpret

• they support compact feature subsets instead of oversized black-box matrices

• they help translate numerical results into design-oriented reasoning

See Also

• Size and Shape Descriptors for geometry, compactness, and planarity

• Electronic Properties Descriptors for frontier orbitals and electronic structure

• Surface Analysis Descriptors for MQSA modes and surface-electronic descriptors

• Basic Concepts for the conceptual overview