Dear all ALPS users,

I want to calculate ground state energy of XXX Heisenberg chain of open boundary conditon with unparallel edge magnetic fields,
i.e.,
H=\sum_{j=1}^{N-1}\sigma_j \sigma_{j+1}
+\frac{1}{p}\sigma_N^z+\frac{1}{q}(\sigma_1^z +\xi\sigma_1^x)
it have sigma^z term in site N, sigma^z and sigma^x terms in site 1.

but the dmrg in ALPS, can not give the correct result. I think the reason is sigma^x term, which lead to the quantity "s_z" doesn't conserve,  as I set the coeffecient of sigma^x to 0, the energy agrees to the data using exact diagonalization very well.

Is DMRG in ALPS able to calculate this unparallel edge magnetic fields model?

My files are below:

LATTICE_LIBRARY="my_lattice.xml"
LATTICE="open chain lattice with special edges 16 "
MODEL="spin"
J=4
SWEEPS=4
NUMBER_EIGENVALUES=1
local_S=0.5
h0=-0.5
Gamma0=-0.0625
h2=0.25
{MAXSTATES=40}

<LATTICES>
 <GRAPH name="open chain lattice with special edges 16" dimension="1" vertices=" 16 " edges="15">
  <VERTEX id="1" type="0"><COORDINATE>0</COORDINATE></VERTEX>
  <VERTEX id="2" type="1"><COORDINATE>2</COORDINATE></VERTEX>
  <VERTEX id="3" type="1"><COORDINATE>3</COORDINATE></VERTEX>
  <VERTEX id="4" type="1"><COORDINATE>4</COORDINATE></VERTEX>
  <VERTEX id="5" type="1"><COORDINATE>5</COORDINATE></VERTEX>
  <VERTEX id="6" type="1"><COORDINATE>6</COORDINATE></VERTEX>
  <VERTEX id="7" type="1"><COORDINATE>7</COORDINATE></VERTEX>
  <VERTEX id="8" type="1"><COORDINATE>8</COORDINATE></VERTEX>
  <VERTEX id="9" type="1"><COORDINATE>9</COORDINATE></VERTEX>
  <VERTEX id="10" type="1"><COORDINATE>10</COORDINATE></VERTEX>
  <VERTEX id="11" type="1"><COORDINATE>11</COORDINATE></VERTEX>
  <VERTEX id="12" type="1"><COORDINATE>12</COORDINATE></VERTEX>
  <VERTEX id="13" type="1"><COORDINATE>13</COORDINATE></VERTEX>
  <VERTEX id="14" type="1"><COORDINATE>14</COORDINATE></VERTEX>
  <VERTEX id="15" type="1"><COORDINATE>15</COORDINATE></VERTEX>
 <VERTEX id="16" type="2"><COORDINATE>16</COORDINATE></VERTEX>
  <EDGE source="1" target="2" id="1" type="0" vector="1"/>
  <EDGE source="2" target="3" id="2" type="0" vector="1"/>
  <EDGE source="3" target="4" id="3" type="0" vector="1"/>
  <EDGE source="4" target="5" id="4" type="0" vector="1"/>
  <EDGE source="5" target="6" id="5" type="0" vector="1"/>
  <EDGE source="6" target="7" id="6" type="0" vector="1"/>
  <EDGE source="7" target="8" id="7" type="0" vector="1"/>
  <EDGE source="8" target="9" id="8" type="0" vector="1"/>
  <EDGE source="9" target="10" id="9" type="0" vector="1"/>
  <EDGE source="10" target="11" id="10" type="0" vector="1"/>
  <EDGE source="11" target="12" id="11" type="0" vector="1"/>
  <EDGE source="12" target="13" id="12" type="0" vector="1"/>
  <EDGE source="13" target="14" id="13" type="0" vector="1"/>
  <EDGE source="14" target="15" id="14" type="0" vector="1"/>
  <EDGE source="15" target="16" id="15" type="0" vector="1"/>
 </GRAPH>
</LATTICES>

the energy of ALPS is : -6.4655612295266689
numerical dialoge data: -27.684359423813586
the difference is large! why?

Best wishes1

Shuai Cui