# QMMM Excited States

### From NWChem

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The excited state QM/MM energy calculations are available with tce and dft levels of theory, the latter is triggered by using "tddft" keyword. | The excited state QM/MM energy calculations are available with tce and dft levels of theory, the latter is triggered by using "tddft" keyword. | ||

The excited state QM/MM gradient energy calculations can be performed only numerically. | The excited state QM/MM gradient energy calculations can be performed only numerically. | ||

{{:qmmm_example4}} | {{:qmmm_example4}} |

## Revision as of 14:29, 18 August 2010

QMMM Single Point Calculations:
Ground State Energy and Gradient |
**Excited State Energy**|
Properties |
ESP

The excited state QM/MM energy calculations are available with tce and dft levels of theory, the latter is triggered by using "tddft" keyword. The excited state QM/MM gradient energy calculations can be performed only numerically.

The example below illustrates single point excited state energy calculation at DFT/B3LYP level 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 tddft nroots 4 notriplet end qmmm bq_zone 3.0 end task qmmm tddft energy