4 Self-Consistent Field Ground-State Methods

4.10 Ground State Method Summary

To summarize the main features of Q-Chem’s ground state self-consistent field capabilities, the user needs to consider:

  • Input a molecular geometry ($molecule keyword)

    • Cartesian

    • Z-matrix

    • Read from prior calculations

  • Declare the job specification ($rem keyword)

    • JOBTYPE

      • *

        Single point

      • *

        Optimization

      • *

        Frequency

      • *

        See Table 4.1 for further options

    • BASIS

      • *

        Refer to Chapter 8 (note: $basis keyword for user defined basis sets)

      • *

        Effective core potentials (if desired); refer to Chapter 8.8

    • METHOD

      • *

        Single method specification for exchange and correlation. Alternatively these can be specified separately.

    • EXCHANGE

      • *

        Linear scaling algorithms for all methods

      • *

        Arsenal of exchange density functionals

      • *

        User definable functionals and hybrids

    • CORRELATION

      • *

        DFT or wave function-based methods

      • *

        Linear scaling (CPU and memory) incorporation of correlation with DFT

      • *

        Arsenal of correlation density functionals

      • *

        User definable functionals and hybrids

      • *

        See Chapter 6 for wave function-based correlation methods.

  • Exploit Q-Chem’s special features

    • CFMM, LinK large molecule options

    • SCF rate of convergence increased through improved guesses and alternative minimization algorithms

    • Explore novel methods if desired: CASE approximation, PAOs.