Excited-State Methods in Q-Chem

Overview of Excited-State Capabilities

Q-Chem offers many excited-state methods, from CIS and TDDFT and their spin-flip variants to the high-level equation-of-motion coupled-cluster (EOM-CC) and the algebraic diagrammatic construction (ADC) methods. The table below summarizes excited-state methods available in Q-Chem.

Method Analytic Gradient Analytic Hessian
Configuration interaction singles
CIS ✓ ✓
RPA ✓ ✓
Extended (X)CIS ✘ ✘
SF-XCIS ✘ ✘
Spin-Adapted XCIS ✘ ✘
CIS with perturbative doubles
CIS(D) ✘ ✘
RI-CIS(D) ✓ ✘
SOS-CIS(D) ✓ ✘
SOS-CIS(D0) ✓ ✘
Time-dependent DFT
TDDFT ✓* ✓*
Spin-Flip (SF) TDDFT ✓ ✘
TDDFT with a Reduced Single-Excitation Space ✓ ✓
∆SCF
MOM ✓ ✓
ROKS with SGM ✓ ✘
Non-orthogonal CI (NOCI)
NOCI ✘ ✘
NOCIS/1C-NOCIS ✘ ✘
Static Exchange (STEX) ✘ ✘
Equation-of-motion coupled cluster theory (EOM-CC)
EOM-EE(SF)-CCSD** ✓*** ✘
EOM-IP(EA)-CCSD** ✓*** ✘
EOM-DIP(DEA)-CCSD** ✘ ✘
EOM-CC/C-PCM ✘ ✘
EOM-CCSD with Core-Valence Separation (CVS) ✘ ✘
Algebraic diagrammatic construction (ADC)
RI-ADC ✘ ✘
Spin Opposite Scaling ADC(2) ✘ ✘
ADC with CVS ✘ ✘
SF-ADC, IP-ADC, EA-ADC ✘ ✘
ADC/SS-PCM ✘ ✘
FDET-ADC ✘ ✘
Restricted active space (RAS)
RAS-CI ✘ ✘
RAS Spin-Flip (SF) ✘ ✘

* Not for all exchange-correlation functionals.

** RI and CD variants are also available.

*** RHF and UHF reference only, including RI and CD implementations.



Properties and Analysis