The MPn method keywords request a Hartree-Fock calculation (by default, RHF for singlets, UHF for higher multiplicities) followed by a Møller-Plesset correlation energy correction [Moller34], truncated at second-order for MP2 [Head-Gordon88a, Saebo89, Frisch90b, Frisch90c, Head-Gordon94], third order for MP3 [Pople76, Pople77], fourth-order for MP4 [Raghavachari78], and fifth-order for MP5 [Raghavachari90]. Analytic gradients are available for MP2 [Pople79, Handy84, Frisch90b, Frisch90c], MP3 and MP4(SDQ) [Trucks88, Trucks88a], and analytic frequencies are available for MP2 [Head-Gordon94]. ROMP2, ROMP3 and ROMP4 energies are also available [Knowles91, Lauderdale91, Lauderdale92].
Gaussian 09 also includes some double hybrid methods which combine exact HF exchange with an MP2-like correlation to a DFT calculation. These methods have the same computational cost as MP2 (rather than that of DFT). Gaussian 09 includes Grimme’s B2PLYP [Grimme06a] and mPW2PLYP [Schwabe06] methods(via keywords of the same name); the empirical dispersion corrected variations are specified by appending a D to the keyword name: e.g., B2PLYPD for B2PLYP with empirical dispersion [Schwabe07]. Energies, gradients and frequencies are available.
MP4(DQ) is specified to use only the space of double and quadruple substitutions, MP4(SDQ) for single, double and quadruple substitutions, or MP4(SDTQ) for full MP4 with single, double, triple and quadruple substitutions [Raghavachari78, Raghavachari80]. Just specifying MP4 defaults to MP4(SDTQ).
The MP5 code has been written for the open shell case only, and so specifying MP5 defaults to a UMP5 calculation. This method requires O3V3 disk storage and scales as O4V4 in cpu time.
FC
All frozen core options are available with this keyword. See the discussion of the FC options for full information.
The appropriate algorithm for MP2 will be selected automatically based on the settings of %Mem and MaxDisk. Thus, the following options are almost never needed (see Efficiency Considerations for more information).
FullDirect
Forces the fully direct algorithm, which requires no external storage beyond that for the SCF. Requires a minimum of 2OVN words of main memory (O=number of occupied orbitals, V=number of virtual orbitals, N=number of basis functions). This is seldom a good choice, except for machines with very large main memory and limited disk.
SemiDirect
Forces the semi-direct algorithm.
Direct
Requests some sort of direct algorithm. The choice between in-core, fully direct and semidirect is made by the program based on memory and disk limits and the dimensions of the problem.
InCore
Forces the in-memory algorithm. This is very fast when it can be used, but requires N4/4 words of memory. It is normally used in conjunction with SCF=InCore. NoInCore prevents the use of the in-core algorithm.
MP2, B2PLYP[D], mPW2PLYP[D] : Energies, analytic gradients, and analytic frequencies.
MP3, MP4(DQ) and MP4(SDQ): Energies, analytic gradients, and numerical frequencies.
MP4(SDTQ) and MP5: Analytic energies, numerical gradients, and numerical frequencies.
RO may be combined with MP2, MP3 and MP4 for energies only.
HF, SCF, Transformation, MaxDisk
Energies. The MP2 energy appears in the output as follows, labeled as EUMP2:
E2= -.3906492545D-01 EUMP2= -.75003727493390D+02
Energies for higher-order Møller-Plesset methods follow. Here is the output from an MP4(SDTQ) calculation:
Time for triples= .04 seconds. MP4(T)= -.55601167D-04 E3= -.10847902D-01 EUMP3= -.75014575395D+02 E4(DQ)= -.32068082D-02 UMP4(DQ)= -.75017782203D+02 E4(SDQ)= -.33238377D-02 UMP4(SDQ)= -.75017899233D+02 E4(SDTQ)= -.33794389D-02 UMP4(SDTQ)= -.75017954834D+02
The energy labeled EUMP3 is the MP3 energy, and the various MP4-level corrections appear after it, with the MP4(SDTQ) output coming in the final line (labeled UMP4(SDTQ)).
Example B2PLYP Output. The B2PLYP energy appears in the output labeled as E(B2PLYP):
E2(B2PLYP) = -0.3262340664D-01 E(B2PLYP) = -0.39113226645200D+02
Last updated on: 10 May 2009