Syntax

FLAGs { $<$flag-statement$>$ } END

is invoked from the main level of X-PLOR. Note: certain energy terms that are initially off will be turned on automatically when statements related to this energy are invoked, but this is generally not the case.

$<$flag-statement$>$:==

EXCLude {$<$*energy-term*$>$ }

excludes specified energy-terms.

INCLude {$<$*energy-term*$>$ }

includes specified energy-terms.

$<$energy-term$>$:==

ANGL

specifies bond angle energy (default: on).

BOND

specifies covalent bond energy (default: on).

CDIH

specifies dihedral angle restraints energy (default: off).

DG

is a distance geometry restraint term (see Chapter 37) (default: off).

DIHE

specifies dihedral angle energy (default: on).

ELEC

specifies intramolecular electrostatic energy (default: on).

HARM

specifies a harmonic energy that restrains the positions of the molecule (default: off).

HBON

specifies explicit hydrogen-bond energy (default: off).

IMPR

specifies improper dihedral angle (e.g., chirality and planarity) energy (default: on).

NCS

specifies non-crystallographic positional restraint energy (default: off).

NOE

specifies distance restraints (see Chapter 20) (default: off).

PELE

specifies symmetry-related electrostatic energy (default: off).

PLAN

specifies planarity restraints energy (default: off).

PVDW

specifies symmetry-related van der Waals energy (default: off).

RELA

is a complete matrix relaxation effective energy term (see Chapter 39) (default: off).

VDW

specifies intramolecular van der Waals energy (default: on).

XREF

specifies crystallographic effective energy (default: off).