4.13 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 7 (note: $basis keyword for user defined basis sets)
  - Effective core potentials (if desired); refer to Chapter 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 5 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.