TURBOMOLE manual
v8.0

Prerequisites

CCSD and CCSD(T) calculations with the pnoccsd module require the same prerequisites as calculations with ccsdf12:

  1. a converged SCF calculation with the one-electron density thres­hold set to $denconv 1.d-5 or less

  2. an auxiliary basis defined in the data group $cbas

  3. if orbitals should be excluded from the correlation treatment the data group $freeze has to be set

  4. the maximum core memory which the program is allowed to allocate should be defined in the data group $maxcor; the recommended value is 66–75% of the available (physical) core memory. (see Sec. 25.2.3 for details)

  5. the data group $pnocsd with a specification of the method and the PNO threshold.

In principle the the data group $pnoccsd does not require more input than a specification of the wavefunction model (available are currently: mp2, mp3, ccsd, ccsd(t0), and ccsd(t)). The program will then use by default a PNO threshold tolpno of \(10^{-7}\). All other thresholds are, if not explicitly specified, coupled to tolpno (see below).

For CCSD(T) calculations one should in addition include the Laplace data group and specify the threshold for the Laplace transformation used in the PNO-based implementation of the perturbative triples correction (T). By default the program will use a threshold of conv=2. In many cases the PNO-CCSD(T0) approximation provides an economic alternative to PNO-CCSD(T).

Calculations at the MP3(F12) or CCSD(F12*) level require in addition:

  • the data group $rir12 with the definition of the standard approximations for the explicitly-correlated contributions (see Sec. 9.5 for details)

  • the data group $lcg, which define the correlation function (here it is in particular important to choose for F12 calculations the exponent; recommended values are 0.9 for cc-pVDZ-F12, 1.0 for cc-pVTZ-F12 and 1.1 for cc-pVQZ-F12 basis sets)

  • a complementary auxiliary (CABS) basis set

Furthermore it is recommeded to select in addition an auxiliary JK basis set for the evaluation of the Fock matrix elements. (The rijk menu of define can be used for this.)