LFOCKACE

From VASP Wiki

LFOCKACE = .TRUE. | .FALSE.
Default: LFOCKACE = .TRUE. 

Default: LFOCKACE = .TRUE. for VASP.6
= N/A for VASP.5.X and older

Description: LFOCKACE determines whether the Adaptively Compressed Exchange Operator is used.[1]

  • N.B.:Available for CPU and OpenACC version of VASP.6 when compiled with -Dfock_dblbuf.

For LFOCKACE=.TRUE. the Cholesky decomposition [math]\displaystyle{ X=LL^\dagger }[/math] of the Fock exchange matrix [math]\displaystyle{ X_{ij} = \langle \tilde\psi_i \mid \tilde V_X \mid \tilde\psi_j \rangle }[/math] is calculated and the adaptively compressed exchange operator [math]\displaystyle{ \tilde V_{ACE} = -\sum_i \mid \tilde X_i \rangle \langle \tilde X_i \mid }[/math] is used for the action of the Fock exchange on the pseudo orbitals. This method can be used for hybrid functionals in combination with the Davidson algorithm (ALGO=Normal) to save a factor of [math]\displaystyle{ \approx 3 }[/math] in computation time.

For LFOCKACE=.FALSE. the conventional orbital representation is used.

Note: it is good scientific practice to cite the original publication (Ref. [1]) if you use this feature. The feature is used by default, if the Davidson algorithm (ALGO = Normal) is used; ACE is not used for ALGO = Damped or ALGO = All.

Related tags and articles

AEXX, AEXX, AGGAX, AGGAC, LHFCALC, List of hybrid functionals, Hybrid functionals: formalism

Examples that use this tag

References