Capabilities

PSI3 can perform ab initio computations employing basis sets of up to 32768 contracted Gaussian-type functions of virtually arbitrary orbital quantum number. PSI3 can recognize and exploit the largest Abelian subgroup of the point group describing the full symmetry of the molecule. Table 2 displays the range of theoretical methods available in PSI3.

Table 2: Summary of theoretical methods available in PSI3.

Method	Energy	Gradient	Hessian
RHF SCF	Y	Y	Y
ROHF SCF	Y	Y	N
UHF SCF	Y	N	N
HF DBOC	Y	N	N
CIS/RPA/TDHF	Y	N	N
TCSCF	Y	Y	N
CASSCF	Y	Y	N
RASSCF	Y	Y	N
RAS-CI	Y	N	N
RAS-CI DBOC	Y	N	N
RHF MP2	Y	Y	N
UHF/ROHF MP2	Y	N	N
RHF MP2-R12	Y	N	N
RHF/UHF/ROHF CCSD	Y	Y	N
RHF/UHF/ROHF CCSD(T)	Y	Y$^*$	N
RHF/UHF/ROHF EOM-CCSD	Y	Y	N

$^*$ CCSD(T) gradients implemented only via an experimental code. A more efficient and robust implementation will appear in the next release.

Geometry optimization (currently restricted to true minima on the potential energy surface) can be performed using either analytic gradients or energy points. Likewise, vibrational frequencies can be computed using analytic second derivatives, by finite differences of analytic gradients, or finite differences of energies. PSI3 can also compute an extensive list of one-electron properties.