# HELIUM

The section that controls optional helium solvent environment (highly experimental, not for general use yet) [Edit on GitHub]

Subsections

- AVERAGES
- CEPERLEY
- COORD
- FORCE
- NNP
- PERM
- PRINT
- RDF
- RHO
- RNG_STATE
- WORM

## Keywords

- SECTION_PARAMETERS

- CELL_SHAPE

- CELL_SIZE

- COORD_INIT_TEMP

- DENSITY

- DROPLET_RADIUS

- GET_FORCES

- HELIUM_ONLY

- INTERACTION_POT_SCAN

- NATOMS

- NBEADS

- NUM_ENV

- N_INNER

- N_OUTER

- PERIODIC

- POTENTIAL_FILE_NAME

- PRESAMPLE

- RNG_SEED

- SAMPLING_METHOD

- SOLUTE_INTERACTION

- SOLUTE_RADIUS

## Keyword descriptions

SECTION_PARAMETERS: logical = F

  Lone keyword: `T`

  Usage: silent

  Whether or not to actually use this section [Edit on GitHub]

CELL_SHAPE: enum = CUBE

  Usage: CELL_SHAPE (CUBE|OCTAHEDRON)

  Valid values:

  - `CUBE`

  - `OCTAHEDRON`

  PBC unit cell shape for helium [Edit on GitHub]

CELL_SIZE: real = [angstrom]

  PBC unit cell size (NOTE 1: density, number of atoms and volume are interdependent - give only two of them; NOTE 2: for small cell sizes specify NATOMS instead) [Edit on GitHub]

COORD_INIT_TEMP: real = 3.00000000E+002 [K]

  Temperature for thermal gaussian initialization of the helium. Negative values correspond to a hot start. [Edit on GitHub]

DENSITY: real = 2.18600000E-002 [angstrom^-3]

  trial density of helium for determining the helium box size [Edit on GitHub]

DROPLET_RADIUS: real = 9.51298235E+307 [angstrom]

  Reject a move if any of the new positions does not lie within this range from the center of gravity [Edit on GitHub]

GET_FORCES: enum = AVERAGE

  Usage: GET_FORCES (AVERAGE|LAST)

  Valid values:

  - `AVERAGE`

  - `LAST`

  Get average MC forces or last MC forces to propagate MD [Edit on GitHub]

HELIUM_ONLY: logical = F

  Lone keyword: `T`

  Simulate helium solvent only, disregard solute entirely [Edit on GitHub]

INTERACTION_POT_SCAN: logical = F

  Lone keyword: `T`

  Scan solute-helium interaction potential, cubefile parameters set in subsection RHO [Edit on GitHub]

NATOMS: integer = 64

  Number of helium atoms [Edit on GitHub]

NBEADS: integer = 25

  Number of helium path integral beads [Edit on GitHub]

NUM_ENV: integer = 1

  Number of independent helium environments [Edit on GitHub]

N_INNER: integer = 6600

  Aliases: INOROT

  Number of MC iterations at the same time slice(s) (number of inner MC loop iterations) [Edit on GitHub]

N_OUTER: integer = 300

  Aliases: IROT

  how often to reselect the time slice(s) to work on (number of outer MC loop iterations) [Edit on GitHub]

PERIODIC: logical = F

  Use periodic boundary conditions for helium [Edit on GitHub]

POTENTIAL_FILE_NAME: string = HELIUM.POT

  Name of the Helium interaction potential file [Edit on GitHub]

PRESAMPLE: logical = F

  Presample He coordinates before first PIMD step [Edit on GitHub]

RNG_SEED: integer = 12345

  Usage: RNG_SEED <INTEGER>

  Initial seed for the (pseudo)random number generator that controls helium coordinate generation and propagation. [Edit on GitHub]

SAMPLING_METHOD: enum = CEPERLEY

  Usage: SAMPLING_METHOD (CEPERLEY|WORM)

  Valid values:

  - `CEPERLEY`

  - `WORM`

  Choose between Ceperley or the worm algorithm [Edit on GitHub]

SOLUTE_INTERACTION: enum = NONE

  Usage: SOLUTE_INTERACTION (NONE | MWATER | NNP)

  Valid values:

  - `NONE` No interaction with solute

  - `MWATER` Test interaction with wrong Water

  - `NNP` Interaction with NNP

  Interaction potential between helium and the solute [Edit on GitHub]

SOLUTE_RADIUS: real = 0.00000000E+000 [angstrom]

  Radius of the solute molecule for prevention of coordinate collision during initialization [Edit on GitHub]