LTMP2 - Tutorial
(UNDER CONSTRUCTION)
On this page, we explain how to perform a calculation using the LTMP2[1] algorithm. Make sure you successfully completed the preparation steps Hartree-Fock ground state and Hartree-Fock virtuals.
The INCAR file
The LTMP2 calculation can simply be performed using the following INCAR file
ALGO = ACFDTRK LMP2LT = .TRUE. NOMEGA = # number of tau points (see below) NBANDS = # same valule as in the Hartree-Fock unoccupieds step ( = number of plane-waves) ENCUT = # same value as in the Hartree-Fock step LORBITALREAL = .TRUE. PRECFOCK = Fast
Make sure that VASP reads the WAVECAR file from the Hartree-Fock virtuals step.
NOMEGA flag
The number of [math]\displaystyle{ \tau }[/math]-points is set with the NOMEGA flag. This is necessary to calculate the Laplace transformed energy denominator (see Ref [1] for details),
[math]\displaystyle{ \frac{1}{\varepsilon_i + \varepsilon_j - \varepsilon_a -\varepsilon_b} = - \int_0^\infty \textrm e^{-(\varepsilon_i + \varepsilon_j - \varepsilon_a -\varepsilon_b)\tau} \; \textrm d \tau \;. }[/math].
Parallelization
The LTMP2 algorithm is a high-performance code and can easily be used on many CPUs. Both OpenMP and MPI is supported.