[AMBER] Assistance with SMD Error Related to Hydrogen Bond Collective Variables

From: Abhisek Jana via AMBER <amber.ambermd.org>
Date: Mon, 27 Oct 2025 11:03:01 +0530

Dear all,

I am performing a steered molecular dynamics (SMD) simulation using
hydrogen bond collective variables defined in the disang.in file.
However, I am encountering the following error:

--------------------------------------------------------------------------------
    3. ATOMIC COORDINATES AND VELOCITIES
--------------------------------------------------------------------------------

default_name
  begin time read from input coords = 103200.000 ps

            Begin reading energy term weight changes/NMR restraints
  WEIGHT CHANGES:
  ERROR: No "wt" namelist with TYPE=END found

                                            I have attached the smd.in
and disang.in files for your reference. I would greatly appreciate your
feedback and suggestions on the possible cause of this error and how to
resolve it.

smd.in

&cntrl
   imin=0, irest=1, ntx=5,
   nstlim=500000, dt=0.002,
   ntc=2, ntf=2, temp0=300.0,
   ntpr=500, ntwx=500, ntwr=5000,
   cut=10.0,
   nmropt=1,
/
DISANG=disang.in
DUMPAVE=mdpull.dat

disang.in

# disang.in--Time-dependent restraints for SMD pulling of 3 H-bonds

# --- Define the restrained atom pairs (Donor-Acceptor)
&rst iat=14468,13467, rk2=5.0, rk3=5.0, r1=0, r2=2.5, r3=2.5, r4=10.0,
ir6=1, ifvar=1 /
&rst iat=14448,13473, rk2=5.0, rk3=5.0, r1=0, r2=2.5, r3=2.5, r4=10.0,
ir6=1, ifvar=2 /
&rst iat=14423,13512, rk2=5.0, rk3=5.0, r1=0, r2=2.5, r3=2.5, r4=10.0,
ir6=1, ifvar=3 /
&rst iat=14429,13492, rk2=5.0, rk3=5.0, r1=0, r2=2.5, r3=2.5, r4=10.0,
ir6=1, ifvar=4 /

# --- Control time-dependent behavior
&wt type='DUMPFREQ', istep1=500 /
&wt type='END' /
&wt type='RAMP', istep1=0, istep2=500000, value1=2.5, value2=10.0,
ivar=1 /
&wt type='RAMP', istep1=0, istep2=500000, value1=2.5, value2=10.0,
ivar=2 /
&wt type='RAMP', istep1=0, istep2=500000, value1=2.5, value2=10.0,
ivar=3 /
&wt type='RAMP', istep1=0, istep2=500000, value1=2.5, value2=10.0,
ivar=4 /
&end

Best regards,

Abhisek Jana

Institute Postdoctoral Fellow

Department of Chemistry, IIT Bombay
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Received on Sun Oct 26 2025 - 23:00:02 PDT
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