extbond (c48b1)
External Bond Module *
by
Pierre-Andre Cazade
Marco Pezzella
Debasish Koner
Markus Meuwly
References:
EXTBOND provides additional bond potential forms, besides the usual
harmonic one provided in CHARMM. The module works by substituting the
harmonic potential of a bond defined in the PSF file for a new
potential and is primarily intended but not limited to applications in
spectroscopy. The PSF remains unchanged. EXTBOND can also add new
bonds, which are not present in the PSF file. Those bonds are not
explicitly added to the PSF file and only exist for the duration of a
References:
[1] Oliver T. Unke and Markus Meuwly, J. Chem. Inf. Model., 2017, 57 (8),
pp 1923–1931
Syntax :: Syntax of the EXTBOND module.
Description :: A brief description of the module and how it works.
Parameter file (optional) :: Shows how to use the parameter file.
Implemented Kernels :: Reproducing kernels available in the module.
How to build the grid :: Brief description of how to build a grid.
Example :: Description of the example: N-Methylacetamide (NMA).
!--------------------------------Syntax--------------------------------!
XTBD { READ UNIT integer }
{ ADDI { HARM k0 (real) r0 (real) } } double selection
{ { AMOE k0 (real) r0 (real) } }
{ { MORS D0 (real) r0 (real) beta (real) } }
{ { QUAR k0 (real) r0 (real) k1 (real) k2 (real) } }
{ { RKHS filename(char) kerneltype(char) asymptote (char)} }
{ REPL { HARM k0 (real) r0 (real) } } double selection
{ { AMOE k0 (real) r0 (real) } }
{ { MORS D0 (real) r0 (real) beta (real) } }
{ { QUAR k0 (real) r0 (real) k1 (real) k2 (real) } }
{ { RKHS filename (char) kerneltype (char) asymptote (char) } }
{ CLEA }
READ option will identify the additional/replacement bonds in the
specified unit file. Information about the input file will be given in
the next section.
ADDI adds bonds between successive atom pairs between the first and
second selections with the potential of choice.
REPL replaces all existing bonds between the first and second
selections with the potential of choice.
CLEA remove any additional/substituting potential.
HARM for a harmonic potential: k0*(r-r0)**2
AMOE for an MM3 anharmonic bond potential used in AMOEBA
MORS for a Morse potential D0*(1-exp(-beta*(r-r0)))**2
QUAR for the quartic potential : k0*(r-r0)**2+k1*(r-r0)**3+k2*(r-r0)**4
RKHS for Reproducing Kernel Hilbert Space: a grid of n points
of distances and energies.
For RKHS the following information are required:
1- The external file is an ordered set of interatomic distances and
energies, described in the "How to build the grid" section. This file
can be given in the csv format or direct as kernels. Notice that the
filename has to be given without extension. The routine checks for
the existence of a ".kernel" file with the specified name, if does not
exist, it will look for the ".csv" and create the new ".kernel" file.
2- Kerneltype: An integer number that describes the type of kernel to
be used. For available kernel types see the "Implemented Kernels"
section below. For additional technical details see reference [1].
3- Asymptote: A real number that rescales the bond energy to the
correct dissociation energy. Due to the kernels implementiation, the
asympotic energy needs to go to zero.
!--------------------------------Description-------------------------------!
EXTBOND is invoked by the XTBD command. At first the module reads the
parameters for the new bond and the atoms involved. The new bond
definition will be considered only for the present run of CHARMM, no
modifications will be applied to the PSF file.
No modifications are needed in the parameter files.
No compatibility issues with other modules in CHARMM are registered.
!-----------------------------Parameter file-----------------------------!
The bond parameters can be given both: internally in the input file or
externally.
The definition of the bond in the external file is presented here.
The first line is an integer number that defines the number of bonds
present in the external file. The second and third lines define the
bond type and atoms involved with its parameters respectively. In the
next lines a dummy example can be found.
N ! number of bonds defined in the file
TYPE ! typology of bond
ATOM1 ATOM2 parameters ! atoms involved in the new bond and bond parameters.
repeat the second and third line N-1 times.
Example::
!--- CHARMM input file
... parameters defintions....
open unit 40 card name yourdatafile
XTBD read unit 40
... the rest of the input
HARM
1 2 600.00 1.23
AMOE
3 4 600.00 1.23
MORS
5 6 120.0 1.21 2.7
QUAR
7 8 110.0 1.2 50. 20.0
RKHS
9 10 pes 0 K1D -121.9746
!-------------------------Implemented Kernels-------------------------!
For more details see reference [1].
0 -> Reciprocal Power N2 M6 Kernel
1 -> Reciprocal Power N3 M6 Kernel
2 -> Reciprocal Power N2 M5 Kernel
3 -> Reciprocal Power N3 M5 Kernel
4 -> Reciprocal Power N2 M4 Kernel
5 -> Reciprocal Power N3 M4 Kernel
6 -> Reciprocal Power N2 M3 Kernel
7 -> Reciprocal Power N3 M3 Kernel
8 -> Reciprocal Power N2 M2 Kernel
9 -> Reciprocal Power N3 M2 Kernel
10 -> Reciprocal Power N2 M1 Kernel
11 -> Reciprocal Power N3 M1 Kernel
12 -> Reciprocal Power N2 M0 Kernel
13 -> Reciprocal Power N3 M0 Kernel
14 -> Exponetial Decay N2 kernel
15 -> Exponetial Decay N2 kernel
N describes the number of terms used in the Kernels, M describes the
degree of the polynomial expansion.
Reciprocal Power Decay:: Those kernels describe a decay of the form of
1/r^(m+1) decay for values larger than the greatest point in the
grid. The kernel is defined for values on the interval [0,infinity).
Laplacian:: Necessary to evaluate the Laplacian kernel given by
exp(||x-x'||/sigma). Note that sigma can be set to any positive
value, but is initialized automatically with the value 1. It is not
recommended for interpolating potential energy surfaces. The kernel is
only defined on the interval [0,infinity).
Exponential Decay:: For values larger than the greatest point in the
grid, the kernel decays exponentially with exp(-beta*x). Note that
beta can be set to any positive value, but is initialized
automatically with the value 1. This type of kernel is recommended
for short-range intermolecular interactions, which often decay
exponentially. The kernel is only defined for values in the interval
[0,infinity).
For most applications a chemical bond can be described by a Reciprocal
Power N2 M6 Kernel (option "0").
!------------------------- How to build a grid-------------------------!
1) For each bond that should be reproduced by a kernel, perform an Ab
Initio calculation along a scan of the bond.
2) Save the bond length and the energies (in AKMA units), in
increasing order of r in a csv file.
r1 , E1
r2 , E2
....
rN , EN
3) Reference the energies to the asymptote E - E_asympt, such that
E(r_asympt)=0.
!-----------------------------------Example-----------------------------------!
The xtbd_nma.inp test case with the parameter xtbd_nma.para parameter
file and the xtbd_pes.csv, that contains the kernel, are distributed
with the package. This example describes the vibrational analysis and
free dynamics of the NMA molecule with the EXTBOND module invoked for
the C=O bond.
by
Pierre-Andre Cazade
Marco Pezzella
Debasish Koner
Markus Meuwly
References:
EXTBOND provides additional bond potential forms, besides the usual
harmonic one provided in CHARMM. The module works by substituting the
harmonic potential of a bond defined in the PSF file for a new
potential and is primarily intended but not limited to applications in
spectroscopy. The PSF remains unchanged. EXTBOND can also add new
bonds, which are not present in the PSF file. Those bonds are not
explicitly added to the PSF file and only exist for the duration of a
References:
[1] Oliver T. Unke and Markus Meuwly, J. Chem. Inf. Model., 2017, 57 (8),
pp 1923–1931
Syntax :: Syntax of the EXTBOND module.
Description :: A brief description of the module and how it works.
Parameter file (optional) :: Shows how to use the parameter file.
Implemented Kernels :: Reproducing kernels available in the module.
How to build the grid :: Brief description of how to build a grid.
Example :: Description of the example: N-Methylacetamide (NMA).
!--------------------------------Syntax--------------------------------!
XTBD { READ UNIT integer }
{ ADDI { HARM k0 (real) r0 (real) } } double selection
{ { AMOE k0 (real) r0 (real) } }
{ { MORS D0 (real) r0 (real) beta (real) } }
{ { QUAR k0 (real) r0 (real) k1 (real) k2 (real) } }
{ { RKHS filename(char) kerneltype(char) asymptote (char)} }
{ REPL { HARM k0 (real) r0 (real) } } double selection
{ { AMOE k0 (real) r0 (real) } }
{ { MORS D0 (real) r0 (real) beta (real) } }
{ { QUAR k0 (real) r0 (real) k1 (real) k2 (real) } }
{ { RKHS filename (char) kerneltype (char) asymptote (char) } }
{ CLEA }
READ option will identify the additional/replacement bonds in the
specified unit file. Information about the input file will be given in
the next section.
ADDI adds bonds between successive atom pairs between the first and
second selections with the potential of choice.
REPL replaces all existing bonds between the first and second
selections with the potential of choice.
CLEA remove any additional/substituting potential.
HARM for a harmonic potential: k0*(r-r0)**2
AMOE for an MM3 anharmonic bond potential used in AMOEBA
MORS for a Morse potential D0*(1-exp(-beta*(r-r0)))**2
QUAR for the quartic potential : k0*(r-r0)**2+k1*(r-r0)**3+k2*(r-r0)**4
RKHS for Reproducing Kernel Hilbert Space: a grid of n points
of distances and energies.
For RKHS the following information are required:
1- The external file is an ordered set of interatomic distances and
energies, described in the "How to build the grid" section. This file
can be given in the csv format or direct as kernels. Notice that the
filename has to be given without extension. The routine checks for
the existence of a ".kernel" file with the specified name, if does not
exist, it will look for the ".csv" and create the new ".kernel" file.
2- Kerneltype: An integer number that describes the type of kernel to
be used. For available kernel types see the "Implemented Kernels"
section below. For additional technical details see reference [1].
3- Asymptote: A real number that rescales the bond energy to the
correct dissociation energy. Due to the kernels implementiation, the
asympotic energy needs to go to zero.
!--------------------------------Description-------------------------------!
EXTBOND is invoked by the XTBD command. At first the module reads the
parameters for the new bond and the atoms involved. The new bond
definition will be considered only for the present run of CHARMM, no
modifications will be applied to the PSF file.
No modifications are needed in the parameter files.
No compatibility issues with other modules in CHARMM are registered.
!-----------------------------Parameter file-----------------------------!
The bond parameters can be given both: internally in the input file or
externally.
The definition of the bond in the external file is presented here.
The first line is an integer number that defines the number of bonds
present in the external file. The second and third lines define the
bond type and atoms involved with its parameters respectively. In the
next lines a dummy example can be found.
N ! number of bonds defined in the file
TYPE ! typology of bond
ATOM1 ATOM2 parameters ! atoms involved in the new bond and bond parameters.
repeat the second and third line N-1 times.
Example::
!--- CHARMM input file
... parameters defintions....
open unit 40 card name yourdatafile
XTBD read unit 40
... the rest of the input
HARM
1 2 600.00 1.23
AMOE
3 4 600.00 1.23
MORS
5 6 120.0 1.21 2.7
QUAR
7 8 110.0 1.2 50. 20.0
RKHS
9 10 pes 0 K1D -121.9746
!-------------------------Implemented Kernels-------------------------!
For more details see reference [1].
0 -> Reciprocal Power N2 M6 Kernel
1 -> Reciprocal Power N3 M6 Kernel
2 -> Reciprocal Power N2 M5 Kernel
3 -> Reciprocal Power N3 M5 Kernel
4 -> Reciprocal Power N2 M4 Kernel
5 -> Reciprocal Power N3 M4 Kernel
6 -> Reciprocal Power N2 M3 Kernel
7 -> Reciprocal Power N3 M3 Kernel
8 -> Reciprocal Power N2 M2 Kernel
9 -> Reciprocal Power N3 M2 Kernel
10 -> Reciprocal Power N2 M1 Kernel
11 -> Reciprocal Power N3 M1 Kernel
12 -> Reciprocal Power N2 M0 Kernel
13 -> Reciprocal Power N3 M0 Kernel
14 -> Exponetial Decay N2 kernel
15 -> Exponetial Decay N2 kernel
N describes the number of terms used in the Kernels, M describes the
degree of the polynomial expansion.
Reciprocal Power Decay:: Those kernels describe a decay of the form of
1/r^(m+1) decay for values larger than the greatest point in the
grid. The kernel is defined for values on the interval [0,infinity).
Laplacian:: Necessary to evaluate the Laplacian kernel given by
exp(||x-x'||/sigma). Note that sigma can be set to any positive
value, but is initialized automatically with the value 1. It is not
recommended for interpolating potential energy surfaces. The kernel is
only defined on the interval [0,infinity).
Exponential Decay:: For values larger than the greatest point in the
grid, the kernel decays exponentially with exp(-beta*x). Note that
beta can be set to any positive value, but is initialized
automatically with the value 1. This type of kernel is recommended
for short-range intermolecular interactions, which often decay
exponentially. The kernel is only defined for values in the interval
[0,infinity).
For most applications a chemical bond can be described by a Reciprocal
Power N2 M6 Kernel (option "0").
!------------------------- How to build a grid-------------------------!
1) For each bond that should be reproduced by a kernel, perform an Ab
Initio calculation along a scan of the bond.
2) Save the bond length and the energies (in AKMA units), in
increasing order of r in a csv file.
r1 , E1
r2 , E2
....
rN , EN
3) Reference the energies to the asymptote E - E_asympt, such that
E(r_asympt)=0.
!-----------------------------------Example-----------------------------------!
The xtbd_nma.inp test case with the parameter xtbd_nma.para parameter
file and the xtbd_pes.csv, that contains the kernel, are distributed
with the package. This example describes the vibrational analysis and
free dynamics of the NMA molecule with the EXTBOND module invoked for
the C=O bond.