Single Point Energy

Overview

A single point (SP) calculation computes the electronic energy and atomic forces at a fixed molecular geometry. Unlike optimization or transition state searches, no atoms are moved during the calculation. The geometry remains exactly as specified in the input, and MAPLE evaluates the energy and gradient at that single configuration.

This is the simplest and fastest task type available in MAPLE, making it the foundation upon which more complex workflows are built.

Usage

The single point task is invoked by including the #sp header command in the input file. No additional parameters are required.

#sp

The #sp command does not accept any method or convergence parameters since there is no iterative procedure involved. You only need to specify the model and device alongside the task command.

Tip

SP is the default task type. If no job type is specified in the input file (i.e., no #sp, #opt, #freq, etc.), MAPLE will automatically perform a single point energy calculation.

Input Example

Below is a complete input file for a single point calculation on a small system using the ANI-1xnr model on a GPU:

#model=ani1xnr
#sp
#device=gpu0

C   0.0  0.0  0.0
H   1.0  0.0  0.0
O   2.0  0.0  0.0

The first three lines are header commands that set the ML model, task type, and compute device. The remaining lines define the atomic coordinates in Cartesian format (element symbol followed by X, Y, Z positions in angstroms).

Parameters

The single point task accepts the following parameter:

Parameter	Type	Default	Description
`verbose`	int	1	Output verbosity level. 0 = energy only, 1 = detailed output with forces, 2 = suppress coordinate printing.

Output

The output file from a single point calculation contains the following information:

Total energy -- reported in Hartree (Eh) units. This is the primary result of the SP calculation.
Gradient / forces -- the atomic forces (negative gradient of the energy with respect to nuclear positions) are computed and printed for each atom.

Example output:

Energy: -10434.811113387317

The energy value represents the total electronic energy of the system at the given geometry as predicted by the specified ML potential.

Use Cases

Single point calculations are useful in a variety of scenarios:

Benchmarking -- comparing energies from different ML models or against reference DFT/ab initio values for the same geometry.
Energy comparisons -- evaluating relative energies of conformers, isomers, or reaction intermediates at their respective geometries.
Post-optimization checks -- verifying the energy at an optimized geometry using a different or higher-level model than was used during optimization.
Force analysis -- examining the magnitude and direction of forces on atoms to assess whether a structure is close to a stationary point.
Workflow building blocks -- SP calculations serve as the fundamental energy/force evaluation used internally by optimization, frequency, TS search, and other iterative tasks.