
Complete Basis Set¶
Code author: Lori A. Burns
Section author: Lori A. Burns
Note
Presently (May 2016), only two of the five delta possibilities are active. Also, temporarily extrapolations are performed on differences of target and scf total energies, rather than on correlation energies directly. This doesn’t affect the extrapolated values of the particular formulas defined here (though it does affect the betas, which are commented out), but it is sloppy and temporary and could affect any user-defined corl extrapolations.
Output¶
At the beginning of a cbs() job is printed a listing of the individual
energy calculations which will be performed. The output snippet below is
from the example job [2] above. It shows first each model chemistry needed
to compute the aggregate model chemistry requested through cbs(). Then,
since, for example, an energy('ccsd(t)')
yields CCSD(T), CCSD, MP2,
and SCF energy values, the wrapper condenses this task list into the second
list of minimum number of calculations which will actually be run.
Naive listing of computations required.
scf / aug-cc-pvqz for SCF TOTAL ENERGY
mp2 / aug-cc-pvtz for MP2 CORRELATION ENERGY
mp2 / aug-cc-pvqz for MP2 CORRELATION ENERGY
ccsd(t) / aug-cc-pvdz for CCSD(T) CORRELATION ENERGY
ccsd(t) / aug-cc-pvtz for CCSD(T) CORRELATION ENERGY
mp2 / aug-cc-pvdz for MP2 CORRELATION ENERGY
mp2 / aug-cc-pvtz for MP2 CORRELATION ENERGY
Enlightened listing of computations required.
mp2 / aug-cc-pvqz for MP2 CORRELATION ENERGY
ccsd(t) / aug-cc-pvdz for CCSD(T) CORRELATION ENERGY
ccsd(t) / aug-cc-pvtz for CCSD(T) CORRELATION ENERGY
At the end of a cbs() job is printed a summary section like the one below. First, in the components section, are listed the results for each model chemistry available, whether required for the cbs job (*) or not. Next, in the stages section, are listed the results for each extrapolation. The energies of this section must be dotted with the weightings in column Wt to get the total cbs energy. Finally, in the CBS section, are listed the results for each stage of the cbs procedure. The stage energies of this section sum outright to the total cbs energy.
==> Components <==
----------------------------------------------------------------------------------
Method / Basis Rqd Energy [H] Variable
----------------------------------------------------------------------------------
scf / aug-cc-pvqz * -1.11916375 SCF TOTAL ENERGY
mp2 / aug-cc-pvqz * -0.03407997 MP2 CORRELATION ENERGY
scf / aug-cc-pvdz -1.11662884 SCF TOTAL ENERGY
mp2 / aug-cc-pvdz * -0.02881480 MP2 CORRELATION ENERGY
ccsd(t) / aug-cc-pvdz * -0.03893812 CCSD(T) CORRELATION ENERGY
ccsd / aug-cc-pvdz -0.03893812 CCSD CORRELATION ENERGY
scf / aug-cc-pvtz -1.11881134 SCF TOTAL ENERGY
mp2 / aug-cc-pvtz * -0.03288936 MP2 CORRELATION ENERGY
ccsd(t) / aug-cc-pvtz * -0.04201004 CCSD(T) CORRELATION ENERGY
ccsd / aug-cc-pvtz -0.04201004 CCSD CORRELATION ENERGY
----------------------------------------------------------------------------------
==> Stages <==
----------------------------------------------------------------------------------
Stage Method / Basis Wt Energy [H] Scheme
----------------------------------------------------------------------------------
scf scf / aug-cc-pvqz 1 -1.11916375 highest_1
corl mp2 / aug-cc-pv[tq]z 1 -0.03494879 corl_xtpl_helgaker_2
delta ccsd(t) / aug-cc-pv[dt]z 1 -0.04330347 corl_xtpl_helgaker_2
delta mp2 / aug-cc-pv[dt]z -1 -0.03460497 corl_xtpl_helgaker_2
----------------------------------------------------------------------------------
==> CBS <==
----------------------------------------------------------------------------------
Stage Method / Basis Energy [H] Scheme
----------------------------------------------------------------------------------
scf scf / aug-cc-pvqz -1.11916375 highest_1
corl mp2 / aug-cc-pv[tq]z -0.03494879 corl_xtpl_helgaker_2
delta ccsd(t) - mp2 / aug-cc-pv[dt]z -0.00869851 corl_xtpl_helgaker_2
total CBS -1.16281105
----------------------------------------------------------------------------------
Extrapolation Schemes¶
Aliases¶
When a particular composite method or its functional form is going to be
reused often, it is convenient to define an alias to it. A convenient
place for such Python code to reside is in psi4/share/python/aliases.py
(source location) or psi4/share/psi/python/aliases.py
(installed
location). No recompilation is necessary after defining an alias. Some
existing examples are below.