NWChem Frequently Asked Questions

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# NWChem FAQ ## QM/MM How do I run a QM/MM calculation? How do I run a QM/MM calculation? You need to have an nwchem input file (example for K(H2O)6), and an associated pdb file (example for K(H2O)6). The PDB file must be complete, containing both the QM and MM atoms. The nwchem input file must contain a prepare section and fields relative to the QM region and the md inputs. A template follows (Note that the memory and eatoms value are only examples.) The example for K(H2O)6 contains comments with more information.
    start SYSTEM

    memory  heap 8 mb  stack 54 mb  global 54 mb

    prepare
       system SYSTEM_CALC
       Define quantum atoms
       Add solvent
       update lists
    end

    basis
       basis set
    end

    scf
       SCF input
       print low
    end

    md
       system SYSTEM_CALC
       MD input
       memory 15000
    end
    qmmm
       eatoms -190.0
    end
    task qmmm scf ( energy | optimize | dynamics )
For detailes on the `eatoms` field, please have a look at the QM/MM section of the Users' Manual. NWChem | Capabilities | Platforms | Download | User's Manual | Programmer's Manual | Release Notes | FAQ Known Bugs | Support | Tutorial | Contributors | Benchmarks | Search | Mol Sci. Soft. Group | Citation Contact: NWChem Support Updated: February 22, 2005