QMMM ESP Charge Analysis

• Example QM/MM ESP Calculation:

The example below illustrates dipole property QM/MM DFT/B3LYP calculation for quantum water molecule embedded into 20 angstrom box of classical SPCE/E water molecules.

The preparation stage that involves definition of the QM region and solvation is performed as part of the calculation. Note that water fragment file wtr.frg is required in this calculation. Prepare run will generate restart file (wtr_ref.rst) and topology file (wtr.top)

In the QM/MM interface block the use of bq_zone value of 3.0 Angstrom is specified.

  start wtr

  permanent_dir ./perm  
  scratch_dir ./data

  prepare  
  source wtr0.pdb  
  new_top new_seq  
  new_rst  
  modify segment 1  quantum  
  center  
  orient  
  solvate box 3.0  
  update lists  
  ignore  
  write wtr_ref.rst  
  write wtr_ref.pdb  
  end

  task prepare

  md  
  system wtr_ref  
  end

  basis  
  * library "6-31G"  
  end

  dft  
  xc b3lyp  
  end

  qmmm  
  bq_zone 3.0  
  end

  property  
   dipole  
  end

  task qmmm dft property