**QUEST** has been designed for molecular electronic structure calculations, with emphasis on density-functional methodologies. Present capabilities include:

- Gaussian and London-Gaussian atomic orbital basis set calculations
- Hartree-Fock Theory
- Kohn-Sham Density-Functional Theory
- Kohn-Sham Current-Density-Functional Theory
- Optimized Effective Potential Density-Functional Theory
- Orbital-Free Density-Functional Theory
- Moller-Plesset (MP) Perturbation Theory: MP2, MP3
- Coupled-cluster Theory: ring-CCD, ladder-CCD, CCD, CCSD, CCSD(T)
- WFT to DFT inversion techniques
*ab initio*Adiabatic Connection calculations- Time-dependent linear response theory at Hartree-Fock and Kohn-Sham levels
- Density-Functional Tight Binding
- Embedded Fragment Method
- Real-time time-dependent theory at Hartree-Fock and Kohn-Sham levels