LMP2 Keywords in the Jaguar Input File

Overview
Examples

The mp2 keyword allows you to request a local Møller-Plesset perturbation theory (LMP2) calculation. By default, LMP2 is off. For more information on the local MP2 method, see Local MP2 Settings and Pseudospectral Local MP2 Techniques. LMP2 keywords are given in Table 1.

Table 1. Keyword settings for local MP2 calculations
Keyword	Value	Description
mp2	0	Do not run LMP2 calculation
	1	Correlate core and valence electrons (not recommended: see text)
	3	Run LMP2 calculation (for valence electrons only)
idelocv	0	Do not delocalize any pairs listed in lmp2 section (default for all calculations except those with iqst>0 and/or ireson>0)
	1	Treat all LMP2 pairs, but delocalize any pairs in lmp2 section as indicated there, or (default for QST-guided transition-state searches) delocalize any pairs on atoms with breaking or forming bonds
	2	Perform a local local MP2 calculation, treating only pairs listed in the lmp2 section at the LMP2 level, and also delocalize any pairs in lmp2 section as indicated there
ireson	0	Do not delocalize LMP2 pairs over other atoms
	1	Delocalize each bond pair in an aromatic ring over the neighboring atoms in the ring
	2	Delocalize bond pairs in an aromatic ring over all atoms in the ring
iheter	0	Treat all atoms with LMP2 if LMP2 is on unless lmp2 section exists; if LMP2 is on and lmp2 section exists, set atom pairs in lmp2 section
	1	Treat only heteroatom pairs (atoms in bonds with atoms of other elements, except C atoms bonded only to C and/or H) and any pairs set in lmp2 section at LMP2 level, other atoms at HF level
loclmp2c	0	Do not localize core orbitals for LMP2 calculation
	1	Perform Boys localization on core orbitals for LMP2 calculation
	2	Perform Pipek-Mezey localization on core orbitals for LMP2 calculation, maximizing Mulliken atomic populations
	3	Perform Pipek-Mezey localization on core orbitals for LMP2 calculation, maximizing Mulliken basis function populations
loclmp2v	1	Perform Boys localization on valence orbitals for LMP2 calculation
	2	Perform Pipek-Mezey localization on valence orbitals for LMP2 calculation, maximizing Mulliken atomic populations
	3	Perform Pipek-Mezey localization on valence orbitals for LMP2 calculation, maximizing Mulliken basis function populations. This scheme produces results that are significantly different from the other two schemes.

LMP2 calculations require a basis set that is set up for the pseudospectral method—see Basis Sets for basis set information. Because the available basis sets are not designed for core correlation, you should not use the mp2=1 setting. Calculations performed with this setting are likely to be misleading. This is because core correlation requires basis functions that have a similar mean radius to the core functions that are correlated, including higher angular momentum functions. For example, to correlate the 1s in a double-zeta basis, an s function and a p function with a similar mean radius to the 1s orbital are needed. The pseudospectral basis sets do not have such functions.

Local MP2 calculations use the LMP2 method for all atoms unless the lmp2 section (described in The lmp2 Section of the Jaguar Input File) is used to set local LMP2 pairs or unless the keyword iheter is set to 1. The iheter and mp2 keyword settings are described in Table 1.

For LMP2 calculations, Jaguar needs to obtain localized orbitals. By default, Jaguar uses the Pipek-Mezey method to perform the localization. If Pipek-Mezey localization does not converge for a particular case, you might want to try Boys localization by changing the settings for the keywords loclmp2c and loclmp2v, as indicated in Table 1. If you are performing a set of calculations to compare against each other, you should use the same localization method for all of the calculations. In particular, the loclmp2v=3 scheme is known to affect the LMP2 energy significantly compared to the other two localization schemes.

By default, the LMP2 method uses an SCF wavefunction calculated with the pseudospectral method. If the SCF calculation is having convergence issues, you may want to set the scf_nops keyword to 1. This setting computes an analytic SCF wavefunction, which is generally more accurate than the pseudospectral SCF wavefunction. The pseudospectral method is still used for the LMP2 calculation.

LMP2 Keywords in the Jaguar Input File

Single Point Energy Examples