MP1 wavefunction

psip_list = mp1_mc {
    sys = system,
    mp1 = {...},
    qmc = {...},
    ccmc = {...},
}

Returns:

a particle_t object.

mp1_mc creates a deterministic MP1 wavefunction and stochastically coarse-grains (rounds down small amplitudes) it into a particle_t object that can be used to initialise a subsequent CCMC calculation. The MP1 wavefunction will be ignored if restarting from a restart file.

Options

sys

type: system object.

Required.

The system on which to perform the calculation. Must be created via a system function.

mp1

type: lua table.

Required.

Further options controlling the calculation.

qmc

type: lua table.

Optional.

If provided, will override the mp1 input options where relevant.

ccmc

type: lua table.

Optional.

If provided, will override the mp1 input options where relevant.

Note

If you wish to chain together a MP1 calculation and a CCMC calculation, one way to do it would be:

sys = {...}
qmc_opt = {...}
ccmc_opt = {...}

psip_list = mp1_mc{
    sys = sys,
    qmc = qmc_opts,
    ccmc = ccmc_opts,
}

ccmc {
    sys = sys,
    qmc = qmc_opts,
    ccmc = ccmc_opts,
    psip_list = psip_list,
    reference = {...},
}

Note the lack of commas after the main tables. This makes sure the MP1 wavefunction (the psip_list object) is compatible with the subsequent CCMC calculation.

MP1 options

D0_population

type: integer.

Required.

Set the initial population on the reference determinant.

Note

This will overwrite the value given in the qmc table.

state_size

type: integer.

Maximum number of excitors to store in the “main” list, which holds the number of particles on the state and related information such as the diagonal Hamiltonian matrix element. The number of elements that can be stored usually should be of the same order as the target population.

If negative, then the absolute value is used as the maximum amount of memory in MB to use for this information.

Note

This will overwrite the value given in the qmc table.

real_amplitudes

type: boolean.

Optional. Default: false.

Allow amplitudes to take non-integer weights. This will often significantly reduce the stochastic noise in the Monte Carlo estimates.

Note

This should be the same as the subsequent calculation.

spawn_cutoff

type: float.

Optional. Default: 0.01.

The threshold for stochastic rounding.

rng_seed

type: integer.

Optional. Default: generate a seed from a hash of the time and calculation UUID.

The seed used to initialise the random number generator.

even_selection

type: boolean.

Optional. Default: false.

Note

Must be true if true in the subsequent CCMC calculation.