Enum RunMode 

pub enum RunMode {
    Normal,
    Read,
    NoRead,
    Stable,
    InterRead,
    CoordinateDrive,
    PathOptimization,
    FixDE,
}

Execution mode for MECP calculations.

Different run modes are optimized for different scenarios, particularly around SCF convergence and wavefunction stability. The choice depends on:

• Whether you’re doing a fresh calculation or restarting
• If you have convergence problems
• If you’re studying open-shell systems
• If you’re doing reaction path following

Variants

Normal

Standard MECP optimization with two-phase workflow

Phase 1: Pre-point calculations WITHOUT checkpoint reading to generate initial wavefunctions Phase 2: Main optimization loop WITH checkpoint reading for faster SCF convergence

Program-specific behavior:

• Gaussian: Generates .chk files in Phase 1, uses guess=read in Phase 2

• ORCA: Generates .gbw files in Phase 1, uses !moread in Phase 2

• XTB: Runs pre-point for initialization, no checkpoint files needed

• BAGEL: Validates model file in Phase 1, uses same model in Phase 2

• Custom: Follows Gaussian-like behavior (depends on interface configuration)

• Recommended for most calculations

• Balanced between speed and robustness

Read

Restart from existing checkpoint file

• Skips pre-point calculations
• Use for restarting interrupted calculations
• Faster start but requires valid checkpoint

NoRead

Fresh SCF at each step (no checkpoint reading)

• Slower but more robust
• Use for difficult SCF convergence
• Helpful when wavefunctions oscillate

Stable

Pre-point calculations for wavefunction stability

• Runs stability checks before optimization
• Use for unstable wavefunctions
• Essential for problematic systems

InterRead

Interleaved reading for open-shell singlets

• Runs state B first, copies to A
• Adds guess=(read,mix) for state A
• Essential for open-shell singlet calculations

CoordinateDrive

Systematically drive a reaction coordinate

• Varies a geometric parameter stepwise
• Generates energy profile along reaction path
• Use with drive_type, drive_atoms, drive_start, drive_end

PathOptimization

Optimize entire reaction path using NEB

• Creates initial path via coordinate driving
• Optimizes using Nudged Elastic Band method
• Identifies transition states and intermediates

FixDE

Constrain energy difference to target value

• Sets target ΔE using fix_de parameter
• Study avoided crossings
• Generate diabatic PES

Trait Implementations

impl Clone for RunMode

fn clone(&self) -> RunMode

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for RunMode

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for RunMode

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for RunMode

fn eq(&self, other: &RunMode) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for RunMode

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Copy for RunMode

impl Eq for RunMode

impl StructuralPartialEq for RunMode