Next-Nearest-Neighbor interaction

[HamidArianZad]

Dear TeNeS establishers,

I would like to simulate the 2D honeycomb lattice with nearest and next-nearest-neighbor interactions J0 and J0'. I considered the interaction parameters in the basic.toml file as:

[model] type = "spin" J0 = 1.0 J0' = 1.0

but I receive below error when I try to run the code:

---

Traceback (most recent call last): File "tutorial_magnetization.py", line 25, in dict_toml = toml.load(f) File "/home/hamid/.local/lib/python3.6/site-packages/toml/decoder.py", line 156, in load return loads(f.read(), _dict, decoder) File "/home/hamid/.local/lib/python3.6/site-packages/toml/decoder.py", line 262, in loads original, i) toml.decoder.TomlDecodeError: Found invalid character in key name: ' ' '. Try quoting the key name. (line 27 column 3 char 319) h

I considered " J0' " instead of J0' and the code works normally. Could you please let me know that " J0' " also indicates the next-nearest-neighbor interaction?

[yomichi]

Please surround J0' with double-quotation marks " as

"J0'" = 1.0

I'm sorry for the document does not mention it. I'll add.

[HamidArianZad]

Hi, I tried to introduce the next-nearest neighbor and that of the next-next-nearest neighbor interactions in tenes_simple file and recall them in basic.toml by putting the corresponding interactions in double-quotation marks but the tenes can not recognize neither next-nearest neighbor " J0' " nor next-next-nearest neighbor " J0'' " interactions. I considered a simple square lattice with next-next-nearest neighbor interaction " J0'' " as introduced in the following codes:

class SquareLattice(Lattice):
    def __init__(self, param: Dict[str, Any]):
        super().__init__(param)
        self.type = "square lattice"
        self.z = 4
        self.skew = 0
        L, W = self.L, self.W
        if W == 1:
            self.skew = 1
        assert L > 1

        self.latticevector = np.diag([L, W])

        vd = self.vdim
        self.sublattice.append(SubLattice([vd, vd, vd, vd], is_vacancy=False))
        self.sublattice.append(SubLattice([vd, vd, vd, vd], is_vacancy=False))
        self.sublattice.append(SubLattice([vd, vd, vd, vd], is_vacancy=False))
        self.sublattice.append(SubLattice([vd, vd, vd, vd], is_vacancy=False))

        for index in range(L * W):
            x, y = index2coord(index, L)
            # if self.initial_states == "antiferro":
            #    if (x + y) % 2 == 0:
            #        self.sublattice[0].add_site(source)
            #    else:
            #        self.sublattice[1].add_site(source)

            if x % 2 == 0 and y % 2 == 0:
                #
                # sublattice A
                #
                self.sublattice[0].add_site(index)
                # self.coords.append(a0 * x + a1 * y)

                # 1st neighbors
                self.bonds[0][0].append(Bond(index, 1, 0))
                self.bonds[0][0].append(Bond(index, 0, 1))

                # 3rd neighbors
                self.bonds[2][0].append(Bond(index, 2, 0))

            elif x % 2 == 1 and y % 2 == 0:
                #
                # sublattice B
                #
                self.sublattice[1].add_site(index)

                # 1st neighbors
                self.bonds[0][0].append(Bond(index, 1, 0))
                self.bonds[0][1].append(Bond(index, 0, 1))

            elif x % 2 == 0 and y % 2 == 1:
                #
                # sublattice C
                #
                self.sublattice[2].add_site(index)

                # 1st neighbors
                self.bonds[0][0].append(Bond(index, 1, 0))
                self.bonds[0][0].append(Bond(index, 0, 1))

                # 3rd neighbors
                self.bonds[2][0].append(Bond(index, 2, 0))
            else:
                #
                # sublattice D 
                #
                self.sublattice[3].add_site(index)
                # 1st neighbors
                self.bonds[0][0].append(Bond(index, 1, 0))
                self.bonds[0][1].append(Bond(index, 0, 1))

And in basic.toml:

[parameter]
[parameter.general]
is_real = true

[parameter.simple_update]
num_step = 100
tau = 0.01

[parameter.full_update]
num_step = 0
tau = 0.01

[parameter.ctm]
iteration_max = 100
dimension = 10

[lattice]
type = "square lattice"
L = 10
W = 2
virtual_dim = 2
initial = "random"

[model]
type = "spin"
J0 = 1
" J0'' " = 2
J1 = 1

I tried several values " J0'' " = [0, 1, 2] but each time I got the same result for the magnetization that seems to be strange. I thing TeNeS does not recognize double-quotation marks for exchange interactions. Can you please address this problem?

[yomichi]

Please drop white spaces from " J0'' " as "J0''". Thank you for reporting. We will make TeNeS automatically strip these whitespaces.

[HamidArianZad]

Thanks! Now it works,

[yomichi]

I'm glad to hear that.