Relativistic Methods

How to initialize Relativistic Calculations?

To perform relativistic calculation in Bagh use the keyword "SPINOR" after the method name in the input file.

Example:

! CCSD SPINOR cc-PVDZ

H 0.0 0.0 0.9168

F 0.0 0.0 0.0

Available Relativistic Routines

• MP2

• CCSD

• CCSD(T)

• FNO-CCSD

• FNO-CCSD(T)

• IP-EOM-CCSD

• IP-EOM-CCSD* and IP-EOM-CCSD-TA*

• CVS-IP-EOM-CCSD

• CVS-IP-EOM-CCSD* and CVS-IP-EOM-CCSD-TA*

• FNO-IP-EOM-CCSD

• FNO-IP-EOM-CCSD* and FNO-IP-EOM-CCSD-TA*

• IP-ADC(1) , IP-ADC(2) , IP-ADC(3)

Customizable Features and Attributes

To perform calculations with desired speed of light, use the keyword light_speed (desired speed of light) in the cc input block.

To include Gaunt or Breit corrections in the calculations use Keywords Gaunt True or Breit True respectively in the cc input block.

for example:

! CCSD SPINOR cc-PVDZ

%cc

Breit True

light_speed 20000

end

H 0.0 0.0 0.9168

F 0.0 0.0 0.0

To use only the real part of the integrals for calculations for molecules with symmetry such that the imaginary part is zero, one can write real_ints True in the cc input block, this reduces computational cost of the process as it stores the integrals as float64 instead of complex128.

example input file:

! CCSD SPINOR cc-PVDZ

%cc

real_ints True

end

H 0.0 0.0 0.9168

F 0.0 0.0 0.0