Function modify_method_for_run_mode 

pub fn modify_method_for_run_mode(
    method: &str,
    program: QMProgram,
    run_mode: RunMode,
) -> String

Dynamically modifies a QM method string based on run mode and program.

This function implements the core logic, adding program-specific keywords and run mode-specific modifications to the method string. This ensures that calculations use the correct keywords for each scenario.

Method Modification Logic

1. Syntax Correction (added for ORCA):

   • Replaces Gaussian-style basis set separators (/) with spaces.
   • E.g., “B3LYP/6-31G*” -> “B3LYP 6-31G*”

2. Program-specific keywords (always added):

   • Gaussian: force (for gradient calculations)
   • ORCA: engrad (for energy and gradient calculations)
   • XTB/BAGEL: No modification needed

3. Stability keywords (added for Stable mode):

   • Gaussian: stable=opt (perform stability analysis and reoptimize if unstable)
   • ORCA: %scf stabperform true StabRestartUHFifUnstable true end (stability analysis)

4. Guess keywords (added for all modes except NoRead):

   • Gaussian: guess=read (read initial guess from checkpoint)
   • ORCA: !moread with %moinp "***" (read molecular orbitals)

Arguments

• method - The base QM method string (e.g., “B3LYP/6-31G*”)
• program - The quantum chemistry program being used
• run_mode - The execution mode for the calculation

Returns

Returns a String containing the modified method with appropriate keywords added.

Examples

use omecp::config::{QMProgram, RunMode};
use omecp::io;

// Normal mode with Gaussian
let modified = io::modify_method_for_run_mode("B3LYP/6-31G*", QMProgram::Gaussian, RunMode::Normal);
assert_eq!(modified, "B3LYP/6-31G* force guess=read");

// Normal mode with ORCA (handling Gaussian syntax)
let modified = io::modify_method_for_run_mode("B3LYP/6-31G*", QMProgram::Orca, RunMode::Normal);
assert!(modified.contains("B3LYP 6-31G*"));
assert!(modified.contains("engrad"));