# MP2 MP3 MP4 MP5These
method keywords request a Hartree-Fock calculation (RHF for singlets, UHF for
higher multiplicities) followed by a Møller-Plesset correlation energy
correction [60], truncated at second-order for **MP2**
[21,22,23,25,65],
third order for **MP3** [61,66],
fourth-order for **MP4** [62], and fifth-order
for **MP5** [64]. Analytic gradients are available
for MP2 [22,23,139,140],
MP3 and MP4(SDQ) [141,142],
and analytic frequencies are available for MP2 [25]. ### AVAILABLE
ALGORITHMS FOR MP2There are four basic algorithms for MP2 calculations
and for producing transformed (MO) integrals on disk: *Semi-Direct*,
which uses both main memory and external (disk) storage as available [23].
This is the default algorithm.
*Direct*, which uses no external
storage by recomputing the integrals as needed during the
transformation.
*Conventional*, which stores the transformed
integrals on disk. This was the only method available
in *Gaussian* *88*, and the only method for generating MO integrals
on disk in *Gaussian* *90*. It is seldom a good choice on any but the
smallest computer systems.
*In-core*, in which all the AO
integrals are generated and stored in main memory, then used without
storing them externally.
The default is to decide between the
in-core, direct, and semi-direct algorithms based on available memory and disk.
The available disk can be specified via the **MaxDisk**
keyword, either in the route section or (preferably) in the **Default.Route**
file. Note that selection of the direct or semi-direct MP2 and transformation
algorithms is separate from selecting direct SCF (which is the default SCF algorithm
in *Gaussian 0*3). The E^{(2)} calculation or transformation then
recomputes integrals as needed in the form required for vectorization. ### VARIATIONS
OF MP4**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 [62,63].
Just specifying **MP4** defaults to **MP4(SDTQ)**.
### LIMITATIONS FOR
MP5The MP5 code has been written for the open shell case only, and so
specifying **MP5** defaults to a **UMP5** calculation. This method requires
O^{3}V^{3} disk storage and scales as O^{4}V^{4}
in cpu time. ### FROZEN-CORE OPTIONS (POST-SCF METHODS)**FC**
The frozen-core options for defining inner-shells to be excluded from the correlation
calculation are valid with these keywords. See the discussion here
for details.
### ALGORITHM SELECTION OPTIONS (MP2 METHODS)Note: The
appropriate algorithm for **MP2** will be selected automatically based on the
settings of **%Mem **and **MaxDisk**.
Thus, these options are almost never needed. **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 N^{4}/4 words of memory.
It is normally used in conjunction with **SCF=InCore**. **NoInCore** prevents
the use of the in-core algorithm.
**MP2**:
Energies, analytic gradients, and analytic frequencies. **ROMP2** is available
for energies only.
**MP3**,** MP4**(**DQ**) and **MP4**(**SDQ**):
Energies, analytic gradients, and numerical frequencies.
**MP4**(**SDTQ**)
and **MP5**: Analytic energies, numerical gradients, and numerical frequencies.
**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 labelled 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)*). |